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Framebuffer驱动程序框架 skeletonfb.c 析分

近来想好好研究一下lcd驱动发开程过，lcd驱动发开重要就是framebuffer的编写了，这里只要想做framebuffer驱动的发开可能这里是必经之路，因为这里这个skeletnfb.c是framebuffer驱动程序发开的骨架，他没有体具去实现任何能功，没有针对任何设备，但是，他的作用却非常惊人，他就是使用说明档文一样，教你怎样一步一步行进framebuffer驱动编写

写贴出这个构架的实现程过，面下再渐渐析分：

这里就开始渐渐啃一啃这个硬骨架吧

/*
* linux/drivers/video/skeletonfb.c -- Skeleton for a frame buffer device
*
* Modified to new api Jan 2001 by James Simmons (jsimmons@transvirtual.com)
*
* Created 28 Dec 1997 by Geert Uytterhoeven
*
*
* I have started rewriting this driver as a example of the upcoming new API
* The primary goal is to remove the console code from fbdev and place it
* into fbcon.c. This reduces the code and makes writing a new fbdev driver
* easy since the author doesn't need to worry about console internals. It
* also allows the ability to run fbdev without a console/tty system on top
* of it.
*
* First the roles of struct fb_info and struct display have changed. Struct
* display will go away. The way the new framebuffer console code will
* work is that it will act to translate data about the tty/console in
* struct vc_data to data in a device independent way in struct fb_info. Then
* various functions in struct fb_ops will be called to store the device
* dependent state in the par field in struct fb_info and to change the
* hardware to that state. This allows a very clean separation of the fbdev
* layer from the console layer. It also allows one to use fbdev on its own
* which is a bounus for embedded devices. The reason this approach works is
* for each framebuffer device when used as a tty/console device is allocated
* a set of virtual terminals to it. Only one virtual terminal can be active
* per framebuffer device. We already have all the data we need in struct
* vc_data so why store a bunch of colormaps and other fbdev specific data
* per virtual terminal.
*
* As you can see doing this makes the con parameter pretty much useless
* for struct fb_ops functions, as it should be. Also having struct
* fb_var_screeninfo and other data in fb_info pretty much eliminates the
* need for get_fix and get_var. Once all drivers use the fix, var, and cmap
* fbcon can be written around these fields. This will also eliminate the
* need to regenerate struct fb_var_screeninfo, struct fb_fix_screeninfo
* struct fb_cmap every time get_var, get_fix, get_cmap functions are called
* as many drivers do now.
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive for
* more details.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/pci.h>
/*
* This is just simple sample code.
* No warranty that it actually compiles.
* Even less warranty that it actually works :-)
*/
/*
* Driver data
*/
static char *mode_option __devinitdata;
/*
* If your driver supports multiple boards, you should make the
* below data types arrays, or allocate them dynamically (using kmalloc()).
*/
/*
*This structure defines the hardware state of the graphics card.Normally
*you place thisina header fileinlinux/include/video.This file usually
*also includes register information.That allows other driver subsystems
* anduserland applications the abilitytouse the same header fileto
*avoid duplicate workandeasy porting of software.
*/
struct xxx_par;
/*
* Here we define the default structs fb_fix_screeninfo and fb_var_screeninfo
* if we don't use modedb. If we do use modedb see xxxfb_init how to use it
* to get a fb_var_screeninfo. Otherwise define a default var as well.
*/
static struct fb_fix_screeninfo xxxfb_fix __devinitdata = {
.id =        "FB's name",
.type =        FB_TYPE_PACKED_PIXELS,
.visual =    FB_VISUAL_PSEUDOCOLOR,
.xpanstep =    1,
.ypanstep =    1,
.ywrapstep = 1,
.accel =    FB_ACCEL_NONE,
};
/*
* Modern graphical hardware not only supports pipelines but some
* also support multiple monitors where each display can have its
* its own unique data. In this case each display could be
* represented by a separate framebuffer device thus a separate
* struct fb_info. Now the struct xxx_par represents the graphics
* hardware state thus only one exist per card. In this case the
* struct xxx_par for each graphics card would be shared between
* every struct fb_info that represents a framebuffer on that card.
* This allows when one display changes it video resolution (info->var)
* the other displays know instantly. Each display can always be
* aware of the entire hardware state that affects it because they share
* the same xxx_par struct. The other side of the coin is multiple
* graphics cards that pass data around until it is finally displayed
* on one monitor. Such examples are the voodoo 1 cards and high end
* NUMA graphics servers. For this case we have a bunch of pars, each
* one that represents a graphics state, that belong to one struct
* fb_info. Their you would want to have *par point to a array of device
* states and have each struct fb_ops function deal with all those
* states. I hope this covers every possible hardware design. If not
* feel free to send your ideas at jsimmons@users.sf.net
*/
/*
* If your driver supports multiple boards or it supports multiple
* framebuffers, you should make these arrays, or allocate them
* dynamically using framebuffer_alloc() and free them with
* framebuffer_release().
*/
static struct fb_info info;
/*
* Each one represents the state of the hardware. Most hardware have
* just one hardware state. These here represent the default state(s).
*/
static struct xxx_par __initdata current_par;
int xxxfb_init(void);
/**
*    xxxfb_open - Optional function. Called when the framebuffer is first accessed.
*    @info: frame buffer structure that represents a single frame buffer
*    @user: tell us if the userland (value=1) or the console is accessing the framebuffer.
*
*Thisfunction isthe firstfunctioncalledinthe framebuffer api.
*Usually you don't needtoprovide thisfunction.Thecasewhere it
*isusedis tochange from a text mode hardware statetoa graphics
*mode state.
*
*    Returns negative errno on error, or zero on success.
*/
static int xxxfb_open(struct fb_info *info, int user)
{
return 0;
}
/**
*    xxxfb_release - Optional function. Called when the framebuffer device is closed.
*    @info: frame buffer structure that represents a single frame buffer
*    @user: tell us if the userland (value=1) or the console is accessing the framebuffer.
*
*Thusfunction iscalled when we close/dev/fborthe framebuffer
*console systemisreleased.Usually you don't need thisfunction.
*Thecasewhere itisusually usedis togo from a graphics state
*toa text mode state.
*
*    Returns negative errno on error, or zero on success.
*/
static int xxxfb_release(struct fb_info *info, int user)
{
return 0;
}
/**
*xxxfb_check_var-Optionalfunction.Validates a var passedin.
*@var:frame buffer variable screen structure
*@info:frame buffer structure that represents a single frame buffer
*    检查我们传入的var是不是是硬件支持的属性，这个法方不变改硬件，也就是fb_info中保存的data不会变改
这个法方用在我们只是想测试一下硬件，但并非真正设置硬件属性
*Checkstoseeifthe hardware supports the state requested by
*var passedin.Thisfunctiondoesnotalter the hardware
*This means the data storedinstruct fb_infoandstruct xxx_pardo
*notchange.This includes the var inside of struct fb_info.
*Do NOTchange these.Thisfunctioncan be calledonits ownifwe
*intenttoonly test a modeand notactuallysetit.The stuffin
*modedb.cisa example of this. Ifthe var passedin isslightly
*off by what the hardware can supportthenwe alter the var PASSEDin
*towhat we cando.
*
* Forvalues that are off,thisfunctionmustroundthem _up_tothe
* nextvalue thatissupported by the hardware. Ifthe valueis
*greater than the highest value supported by the hardware, thenthis
* functionmust return-EINVAL.
*
*Exceptiontothe above rule:Some drivers have a fixed mode,ie,
*the hardwareisalreadysetat boot up, andcannot be changed. In
*thiscase,itismore acceptable that thisfunctionjust return
*a copy of the currently working var(info->var).Betteris to not
*implement thisfunction,as the upper layer willdothe copying
*of the current varforyou.
*
*Note:Thisisthe onlyfunctionwhere the contents of var can be
*freely adjusted after the driver has been registered. Ifyou find
*that you have code outside of thisfunctionthat alters the content
*of var, thenyou are doing something wrong.Note also that the
*contents of info->var must beleftuntouched at all times after
*driver registration.
*
*    Returns negative errno on error, or zero on success.
*/
static int xxxfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
/* ... */
return 0;
}
/**
*xxxfb_set_par-Optionalfunction.Alters the hardware state.
*@info:frame buffer structure that represents a single frame buffer
*使用这个法方是用来设置framebuffer属性的，会变改fb_info中的par和fb_fix_screeinfo数据，
但是不变改var的数据
*Using the fb_var_screeninfoinfb_info wesetthe resolution of the
*this particular framebuffer.Thisfunctionalters the parANDthe
*fb_fix_screeninfo storedinfb_info.It doesn'tnotalter varin
*fb_info since we are using that data.This means we dependonthe
*datainvar inside fb_infotobe supported by the hardware.
*
*Thisfunction isalso usedtorecover/restore the hardwaretoa
*known working state.
*
*xxxfb_check_varisalways called before xxxfb_set_partoensure that
*the contents of varisalways valid.
*
*Againifyou can't change the resolution you don't need thisfunction.
*
*However,evenifyour hardware doesnotsupport mode changing,
*a set_par might be neededtoat least initialize the hardwareto
*a known working state,especiallyifit came back from another
*process that also modifies the same hardware,such as X.
*
* Ifthisisthecase,a combination such as the following should work:
*
*staticintxxxfb_check_var(struct fb_var_screeninfo*var,
*struct fb_info*info)
* {
* *var=info->var;
*return 0;
* }
*
*staticintxxxfb_set_par(struct fb_info*info)
* {
*init your hardware here
* }
*
*    Returns negative errno on error, or zero on success.
*/
static int xxxfb_set_par(struct fb_info *info)
{
struct xxx_par *par = info->par;
/* ... */
return 0;
}
/**
*     xxxfb_setcolreg - Optional function. Sets a color register.
* @regno: Which register in the CLUT we are programming
* @red: The red value which can be up to 16 bits wide
*    @green: The green value which can be up to 16 bits wide
*    @blue: The blue value which can be up to 16 bits wide.
*    @transp: If supported, the alpha value which can be up to 16 bits wide.
* @info: frame buffer info structure
*
*Seta single color register.The values supplied have a 16 bit
*magnitude which needstobe scaledinthisfunction forthe hardware.
*Thingstotake into consideration are how many color registers, if
*any,are supported with the current color visual.With truecolor mode
*no color palettes are supported.Here a pseudo paletteiscreated
*which we store the valueinpseudo_paletteinstruct fb_info. For
*pseudocolor mode we have a limited color palette. Todeal with this
*we can program what colorisdisplayedfora particular pixel value.
*DirectColorissimilarinthat we can programeachcolor field. If
*we have a static colormap we don't needtoimplement thisfunction.
*
*    Returns negative errno on error, or zero on success.
*/
static int xxxfb_setcolreg(unsigned regno, unsigned red, unsigned green,
unsigned blue, unsigned transp,
struct fb_info *info)
{
if (regno >= 256) /* no. of hw registers */
return -EINVAL;
/*
* Program hardware... do anything you want with transp
*/
/* grayscale works only partially under directcolor */
if (info->var.grayscale) {
/* grayscale = 0.30*R + 0.59*G + 0.11*B */
red = green = blue = (red * 77 + green * 151 + blue * 28) >> 8;
}
/* Directcolor:
* var->{color}.offset contains start of bitfield
* var->{color}.length contains length of bitfield
* {hardwarespecific} contains width of DAC
* pseudo_palette[X] is programmed to (X << red.offset) |
* (X << green.offset) |
* (X << blue.offset)
* RAMDAC[X] is programmed to (red, green, blue)
* color depth = SUM(var->{color}.length)
*
*     Pseudocolor:
* var->{color}.offset is 0 unless the palette index takes less than
* bits_per_pixel bits and is stored in the upper
* bits of the pixel value
* var->{color}.length is set so that 1 << length is the number of
* available palette entries
* pseudo_palette is not used
* RAMDAC[X] is programmed to (red, green, blue)
* color depth = var->{color}.length
*
*     Static pseudocolor:
* same as Pseudocolor, but the RAMDAC is not programmed (read-only)
*
*     Mono01/Mono10:
* Has only 2 values, black on white or white on black (fg on bg),
* var->{color}.offset is 0
* white = (1 << var->{color}.length) - 1, black = 0
* pseudo_palette is not used
* RAMDAC does not exist
* color depth is always 2
*
*     Truecolor:
* does not use RAMDAC (usually has 3 of them).
* var->{color}.offset contains start of bitfield
* var->{color}.length contains length of bitfield
* pseudo_palette is programmed to (red << red.offset) |
* (green << green.offset) |
* (blue << blue.offset) |
* (transp << transp.offset)
* RAMDAC does not exist
* color depth = SUM(var->{color}.length})
*
*     The color depth is used by fbcon for choosing the logo and also
*     for color palette transformation if color depth < 4
*
*    As can be seen from the above, the field bits_per_pixel is _NOT_
*    a criteria for describing the color visual.
*
*    A common mistake is assuming that bits_per_pixel <= 8 is pseudocolor,
*    and higher than that, true/directcolor. This is incorrect, one needs
*    to look at the fix->visual.
*
*     Another common mistake is using bits_per_pixel to calculate the color
*     depth. The bits_per_pixel field does not directly translate to color
*     depth. You have to compute for the color depth (using the color
*     bitfields) and fix->visual as seen above.
*/
/*
*     This is the point where the color is converted to something that
*     is acceptable by the hardware.
*/
#define CNVT_TOHW(val,width) ((((val)<<(width))+0x7FFF-(val))>>16)
red = CNVT_TOHW(red, info->var.red.length);
green = CNVT_TOHW(green, info->var.green.length);
blue = CNVT_TOHW(blue, info->var.blue.length);
transp = CNVT_TOHW(transp, info->var.transp.length);
#undef CNVT_TOHW
/*
* This is the point where the function feeds the color to the hardware
* palette after converting the colors to something acceptable by
* the hardware. Note, only FB_VISUAL_DIRECTCOLOR and
* FB_VISUAL_PSEUDOCOLOR visuals need to write to the hardware palette.
* If you have code that writes to the hardware CLUT, and it's not
* any of the above visuals, then you are doing something wrong.
*/
if (info->fix.visual == FB_VISUAL_DIRECTCOLOR ||
info->fix.visual == FB_VISUAL_TRUECOLOR)
write_{red|green|blue|transp}_to_clut();
/*This is the point were you need to fill up the contents of
* info->pseudo_palette. This structure is used _only_ by fbcon, thus
* it only contains 16 entries to match the number of colors supported
* by the console. The pseudo_palette is used only if the visual is
* in directcolor or truecolor mode. With other visuals, the
* pseudo_palette is not used. (This might change in the future.)
*
* The contents of the pseudo_palette is in raw pixel format. Ie, each
* entry can be written directly to the framebuffer without any conversion.
* The pseudo_palette is (void *). However, if using the generic
* drawing functions (cfb_imageblit, cfb_fillrect), the pseudo_palette
* must be casted to (u32 *) _regardless_ of the bits per pixel. If the
* driver is using its own drawing functions, then it can use whatever
* size it wants.
*/
if (info->fix.visual == FB_VISUAL_TRUECOLOR ||
info->fix.visual == FB_VISUAL_DIRECTCOLOR) {
u32 v;
if (regno >= 16)
return -EINVAL;
v = (red << info->var.red.offset) |
(green << info->var.green.offset) |
(blue << info->var.blue.offset) |
(transp << info->var.transp.offset);
((u32*)(info->pseudo_palette))[regno] = v;
}
/* ... */
return 0;
}
/**
* xxxfb_pan_display - NOT a required function. Pans the display.
* @var: frame buffer variable screen structure
* @info: frame buffer structure that represents a single frame buffer
*
* Pan (or wrap, depending on the `vmode' field) the display using the
* 'xoffset' and `yoffset' fields of the `var' structure.
* If the values don't fit, return -EINVAL.
*
* Returns negative errno on error, or zero on success.
*/
static int xxxfb_pan_display(struct fb_var_screeninfo *var,
struct fb_info *info)
{
/*
* If your hardware does not support panning, _do_ _not_ implement this
* function. Creating a dummy function will just confuse user apps.
*/
/*
* Note that even if this function is fully functional, a setting of
* 0 in both xpanstep and ypanstep means that this function will never
* get called.
*/
/* ... */
return 0;
}
/**
* xxxfb_blank - NOT a required function. Blanks the display.
* @blank_mode: the blank mode we want.
* @info: frame buffer structure that represents a single frame buffer
*
* Blank the screen if blank_mode != FB_BLANK_UNBLANK, else unblank.
* Return 0 if blanking succeeded, != 0 if un-/blanking failed due to
* e.g. a video mode which doesn't support it.
*
* Implements VESA suspend and powerdown modes on hardware that supports
* disabling hsync/vsync:
*
* FB_BLANK_NORMAL = display is blanked, syncs are on.
* FB_BLANK_HSYNC_SUSPEND = hsync off
* FB_BLANK_VSYNC_SUSPEND = vsync off
* FB_BLANK_POWERDOWN = hsync and vsync off
*
* If implementing this function, at least support FB_BLANK_UNBLANK.
* Return !0 for any modes that are unimplemented.
*
*/
static int xxxfb_blank(int blank_mode, struct fb_info *info)
{
/* ... */
return 0;
}
/* ------------ Accelerated Functions --------------------- */
/*
* We provide our own functions if we have hardware acceleration
* or non packed pixel format layouts. If we have no hardware
* acceleration, we can use a generic unaccelerated function. If using
* a pack pixel format just use the functions in cfb_*.c. Each file
* has one of the three different accel functions we support.
*/
/**
* xxxfb_fillrect - REQUIRED function. Can use generic routines if
*              non acclerated hardware and packed pixel based.
*             Draws a rectangleonthe screen.
*
* @info: frame buffer structure that represents a single frame buffer
*    @region: The structure representing the rectangular region we
*         wish to draw to.
*
*    This drawing operation places/removes a retangle on the screen
*    depending on the rastering operation with the value of color which
*    is in the current color depth format.
*/
void xxxfb_fillrect(struct fb_info *p, const struct fb_fillrect *region)
{
/*    Meaning of struct fb_fillrect
*
*    @dx: The x and y corrdinates of the upper left hand corner of the
*    @dy: area we want to draw to.
*    @width: How wide the rectangle is we want to draw.
*    @height: How tall the rectangle is we want to draw.
*    @color:    The color to fill in the rectangle with.
*    @rop: The raster operation. We can draw the rectangle with a COPY
*     of XOR which provides erasing effect.
*/
}
/**
* xxxfb_copyarea - REQUIRED function. Can use generic routines if
* non acclerated hardware and packed pixel based.
* Copies one area of the screentoanother area.
*
* @info: frame buffer structure that represents a single frame buffer
* @area: Structure providing the data to copy the framebuffer contents
*     from one region to another.
*
* This drawing operation copies a rectangular area from one area of the
*    screen to another area.
*/
void xxxfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
{
/*
* @dx: The x and y coordinates of the upper left hand corner of the
*    @dy: destination area on the screen.
* @width: How wide the rectangle is we want to copy.
* @height: How tall the rectangle is we want to copy.
* @sx: The x and y coordinates of the upper left hand corner of the
* @sy: source area on the screen.
*/
}
/**
* xxxfb_imageblit - REQUIRED function. Can use generic routines if
* non acclerated hardware and packed pixel based.
* Copies a image from system memorytothe screen.
*
* @info: frame buffer structure that represents a single frame buffer
*    @image:    structure defining the image.
*
* This drawing operation draws a image on the screen. It can be a
*    mono image (needed for font handling) or a color image (needed for
*    tux).
*/
void xxxfb_imageblit(struct fb_info *p, const struct fb_image *image)
{
/*
* @dx: The x and y coordinates of the upper left hand corner of the
*    @dy: destination area to place the image on the screen.
* @width: How wide the image is we want to copy.
* @height: How tall the image is we want to copy.
* @fg_color: For mono bitmap images this is color data for
* @bg_color: the foreground and background of the image to
*         write directly to the frmaebuffer.
*    @depth:    How many bits represent a single pixel for this image.
*    @data: The actual data used to construct the image on the display.
*    @cmap: The colormap used for color images.
*/
/*
* The generic function, cfb_imageblit, expects that the bitmap scanlines are
* padded to the next byte. Most hardware accelerators may require padding to
* the next u16 or the next u32. If that is the case, the driver can specify
* this by setting info->pixmap.scan_align = 2 or 4. See a more
* comprehensive description of the pixmap below.
*/
}
/**
*    xxxfb_cursor -     OPTIONAL. If your hardware lacks support
*            for a cursor, leave this field NULL.
*
* @info: frame buffer structure that represents a single frame buffer
*    @cursor: structure defining the cursor to draw.
*
* This operationisusedto set oralter the properities of thecursor.
*
*    Returns negative errno on error, or zero on success.
*/
int xxxfb_cursor(struct fb_info *info, struct fb_cursor *cursor)
{
/*
* @set:     Which fields we are altering in struct fb_cursor
*    @enable: Disable or enable the cursor
* @rop:     The bit operation we want to do.
* @mask: This is the cursor mask bitmap.
* @dest: A image of the area we are going to display the cursor.
*        Used internally by the driver.
* @hot:    The hot spot.
*    @image:    The actual data for the cursor image.
*
* NOTES ON FLAGS (cursor->set):
*
* FB_CUR_SETIMAGE - the cursor image has changed (cursor->image.data)
* FB_CUR_SETPOS - the cursor position has changed (cursor->image.dx|dy)
* FB_CUR_SETHOT - the cursor hot spot has changed (cursor->hot.dx|dy)
* FB_CUR_SETCMAP - the cursor colors has changed (cursor->fg_color|bg_color)
* FB_CUR_SETSHAPE - the cursor bitmask has changed (cursor->mask)
* FB_CUR_SETSIZE - the cursor size has changed (cursor->width|height)
* FB_CUR_SETALL - everything has changed
*
* NOTES ON ROPs (cursor->rop, Raster Operation)
*
* ROP_XOR - cursor->image.data XOR cursor->mask
* ROP_COPY - curosr->image.data AND cursor->mask
*
* OTHER NOTES:
*
* - fbcon only supports a 2-color cursor (cursor->image.depth = 1)
* - The fb_cursor structure, @cursor, _will_ always contain valid
* fields, whether any particular bitfields in cursor->set is set
* or not.
*/
}
/**
*    xxxfb_rotate - NOT a required function. If your hardware
*            supports rotation the whole screen then
*            you would provide a hook for this.
*
* @info: frame buffer structure that represents a single frame buffer
*    @angle: The angle we rotate the screen.
*
* This operation is used to set or alter the properities of the
*    cursor.
*/
void xxxfb_rotate(struct fb_info *info, int angle)
{
/* Will be deprecated */
}
/**
*    xxxfb_sync - NOT a required function. Normally the accel engine
*         for a graphics card take a specific amount of time.
*         Often we have to wait for the accelerator to finish
*         its operation before we can write to the framebuffer
*         so we can have consistent display output.
*
* @info: frame buffer structure that represents a single frame buffer
*
* If the driver has implemented its own hardware-based drawing function,
* implementing this function is highly recommended.
*/
int xxxfb_sync(struct fb_info *info)
{
return 0;
}
/*
* Frame buffer operations
*/
static struct fb_ops xxxfb_ops= {
.owner=THIS_MODULE,
.fb_open=xxxfb_open,
.fb_read=xxxfb_read,
.fb_write=xxxfb_write,
.fb_release=xxxfb_release,
.fb_check_var=xxxfb_check_var,
.fb_set_par=xxxfb_set_par,
.fb_setcolreg=xxxfb_setcolreg,
.fb_blank=xxxfb_blank,
.fb_pan_display=xxxfb_pan_display,
.fb_fillrect=xxxfb_fillrect,/*Needed!!! */
.fb_copyarea=xxxfb_copyarea,/*Needed!!! */
.fb_imageblit=xxxfb_imageblit,/*Needed!!! */
.fb_cursor=xxxfb_cursor,/*Optional!!! */
.fb_rotate=xxxfb_rotate,
.fb_sync=xxxfb_sync,
.fb_ioctl=xxxfb_ioctl,
.fb_mmap=xxxfb_mmap,
};
/* ------------------------------------------------------------------------- */
/*
* Initialization
*/
这里他们的定义是不一样的，唯一的不同
/*staticint__init xxfb_probe(struct platform_device*pdev) -- forplatform devs*/
staticint__devinit xxxfb_probe(struct pci_dev*dev,conststruct pci_device_id*ent)
{
struct fb_info *info;
struct xxx_par *par;
struct device *device = &dev->dev; /* or &pdev->dev */
int cmap_len, retval;
/*
* Dynamically allocate info and par
*/
info=framebuffer_alloc(sizeof(struct xxx_par),device);
if (!info) {
/* goto error path */
}
par=info->par;把我们驱动中的私有数据指向info->par，我们在上面已经通过framebuffer_alloc为他申请了内存
/*
* Here we set the screen_base to the virtual memory address
* for the framebuffer. Usually we obtain the resource address
* from the bus layer and then translate it to virtual memory
* space via ioremap. Consult ioport.h.
*/
这里注释也已经说的很清楚了，我们通常通过注册好的设备信息获取到memory address，然后把这个地址转换为virtual memory通过ioremap这个法方
info->screen_base=framebuffer_virtual_memory;
info->fbops= &xxxfb_ops;这个定义好的xxxfb_ops结构中包含了用户空间访问driver的所有法方，用户访问/dev/fb0最终通过fbmem中注册的法方调用这里的法方
info->fix =xxxfb_fix; /*this will be the onlytimexxxfb_fix will beused,so mark it as __devinitdata*/
info->pseudo_palette=pseudo_palette; /*The pseudopaletteisan16-memberarray*/
/*
* Setup flagstoindicate what sort of acceleration your
*driver can provide(pan/wrap/copyarea/etc.) andwhether it
* isa module--see FBINFO_* ininclude/linux/fb.h
*
* If your hardware can support any of the hardware accelerated functions
* fbcon performance will improve if info->flags is set properly.
*
* FBINFO_HWACCEL_COPYAREA - hardware moves
* FBINFO_HWACCEL_FILLRECT - hardware fills
* FBINFO_HWACCEL_IMAGEBLIT - hardware mono->color expansion
* FBINFO_HWACCEL_YPAN - hardware can pan display in y-axis
* FBINFO_HWACCEL_YWRAP - hardware can wrap display in y-axis
* FBINFO_HWACCEL_DISABLED - supports hardware accels, but disabled
* FBINFO_READS_FAST - if set, prefer moves over mono->color expansion
* FBINFO_MISC_TILEBLITTING - hardware can do tile blits
*
* NOTE: These are for fbcon use only.
*/
info->flags=FBINFO_DEFAULT;
/********************* This stage is optional ******************************/
/*
* The struct pixmap is a scratch pad for the drawing functions. This
* is where the monochrome bitmap is constructed by the higher layers
* and then passed to the accelerator. For drivers that uses
* cfb_imageblit, you can skip this part. For those that have a more
* rigorous requirement, this stage is needed
*/
/* PIXMAP_SIZE should be small enough to optimize drawing, but not
* large enough that memory is wasted. A safe size is
* (max_xres * max_font_height/8). max_xres is driver dependent,
* max_font_height is 32.
*/
info->pixmap.addr = kmalloc(PIXMAP_SIZE, GFP_KERNEL);
if (!info->pixmap.addr) {
/* goto error */
}
info->pixmap.size = PIXMAP_SIZE;
/*
* FB_PIXMAP_SYSTEM - memory is in system ram
* FB_PIXMAP_IO - memory is iomapped
* FB_PIXMAP_SYNC - if set, will call fb_sync() per access to pixmap,
* usually if FB_PIXMAP_IO is set.
*
* Currently, FB_PIXMAP_IO is unimplemented.
*/
info->pixmap.flags = FB_PIXMAP_SYSTEM;
/*
* scan_align is the number of padding for each scanline. It is in bytes.
* Thus for accelerators that need padding to the next u32, put 4 here.
*/
info->pixmap.scan_align = 4;
/*
* buf_align is the amount to be padded for the buffer. For example,
* the i810fb needs a scan_align of 2 but expects it to be fed with
* dwords, so a buf_align = 4 is required.
*/
info->pixmap.buf_align = 4;
/* access_align is how many bits can be accessed from the framebuffer
* ie. some epson cards allow 16-bit access only. Most drivers will
* be safe with u32 here.
*
* NOTE: This field is currently unused.
*/
info->pixmap.access_align = 32;
/***************************** End optional stage ***************************/
/*
*This should give a reasonable default video mode.The followingis
*done when we canseta video mode.
*/
if (!mode_option)
mode_option = "640x480@60";
retval = fb_find_mode(&info->var, info, mode_option, NULL, 0, NULL, 8);
if (!retval || retval == 4)
return -EINVAL;
/* This has to be */
if (fb_alloc_cmap(&info->cmap, cmap_len, 0))
return -ENOMEM;
/*
*The followingisdoneinthecaseof having hardware with a static
*mode. Ifwe are setting the mode ourselves we don'tcallthis.
*/
info->var = xxxfb_var;
/*
* For drivers that can...
*/
xxxfb_check_var(&info->var,info);
/*
*Does acall tofb_set_par()before register_framebuffer needed?This
*will dependonyouandthe hardware. Ifyou are sure that your driver
* isthe only deviceinthe system,acall tofb_set_par() issafe.
*
*Hardwareinx86 systems has a VGA core.Calling set_par()at this
*point will corrupt the VGA console,so it might be safertoskip a
* call toset_par hereandjust allow fbconto doitforyou.
*/
/* xxxfb_set_par(info); */
if (register_framebuffer(info) <0) {注册设备，fbmem中负责注册了一个fb 字符设备，只有调用了这个法方，才真正创建了这个fb字符设备
fb_dealloc_cmap(&info->cmap);
return -EINVAL;
}
printk(KERN_INFO "fb%d: %s frame buffer device\n", info->node,
info->fix.id);
pci_set_drvdata(dev,info); /* orplatform_set_drvdata(pdev,info) */方便后面使用info这个结构中的所有数据
return 0;
}
/*
* Cleanup
*/
/* static void __devexit xxxfb_remove(struct platform_device *pdev) */
static void __devexit xxxfb_remove(struct pci_dev *dev)
{
struct fb_info *info = pci_get_drvdata(dev);
/* or platform_get_drvdata(pdev); */
if (info) {
unregister_framebuffer(info);
fb_dealloc_cmap(&info->cmap);
/* ... */
framebuffer_release(info);
}
}
#ifdef CONFIG_PCI
#ifdef CONFIG_PM
/**
*    xxxfb_suspend - Optional but recommended function. Suspend the device.
*    @dev: PCI device
*    @msg: the suspend event code.
*
* See Documentation/power/devices.txt for more information
*/
static int xxxfb_suspend(struct pci_dev *dev, pm_message_t msg)
{
struct fb_info *info = pci_get_drvdata(dev);
struct xxxfb_par *par = info->par;
/* suspend here */
return 0;
}
/**
*    xxxfb_resume - Optional but recommended function. Resume the device.
*    @dev: PCI device
*
* See Documentation/power/devices.txt for more information
*/
static int xxxfb_resume(struct pci_dev *dev)
{
struct fb_info *info = pci_get_drvdata(dev);
struct xxxfb_par *par = info->par;
/* resume here */
return 0;
}
#else
#define xxxfb_suspend NULL
#define xxxfb_resume NULL
#endif /* CONFIG_PM */
static struct pci_device_id xxxfb_id_table[] = {
{ PCI_VENDOR_ID_XXX, PCI_DEVICE_ID_XXX,
PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY << 16,
PCI_CLASS_MASK, 0 },
{ 0, }
};
/* For PCI drivers */
static struct pci_driver xxxfb_driver = {
.name =        "xxxfb",
.id_table=xxxfb_id_table,
.probe =    xxxfb_probe,
.remove =    __devexit_p(xxxfb_remove),
.suspend = xxxfb_suspend, /* optional but recommended */
.resume = xxxfb_resume, /* optional but recommended */
};
MODULE_DEVICE_TABLE(pci, xxxfb_id_table);
int __init xxxfb_init(void)
{
/*
* For kernel boot options (in 'video=xxxfb:<options>' format)
*/
#ifndef MODULE
char *option = NULL;
if (fb_get_options("xxxfb", &option))
return -ENODEV;
xxxfb_setup(option);
#endif
return pci_register_driver(&xxxfb_driver);
}
static void __exit xxxfb_exit(void)
{
pci_unregister_driver(&xxxfb_driver);
}
#else /*non PCI,platform drivers*/
#include <linux/platform_device.h>
/* for platform devices */
#ifdef CONFIG_PM
/**
*    xxxfb_suspend - Optional but recommended function. Suspend the device.
*    @dev: platform device
*    @msg: the suspend event code.
*
* See Documentation/power/devices.txt for more information
*/
static int xxxfb_suspend(struct platform_device *dev, pm_message_t msg)
{
struct fb_info *info = platform_get_drvdata(dev);
struct xxxfb_par *par = info->par;
/* suspend here */
return 0;
}
/**
*    xxxfb_resume - Optional but recommended function. Resume the device.
*    @dev: platform device
*
* See Documentation/power/devices.txt for more information
*/
static int xxxfb_resume(struct platform_dev *dev)
{
struct fb_info *info = platform_get_drvdata(dev);
struct xxxfb_par *par = info->par;
/* resume here */
return 0;
}
#else
#define xxxfb_suspend NULL
#define xxxfb_resume NULL
#endif /* CONFIG_PM */
static struct platform_device_driver xxxfb_driver = {
.probe = xxxfb_probe,
.remove = xxxfb_remove,
.suspend = xxxfb_suspend, /* optional but recommended */
.resume = xxxfb_resume, /* optional but recommended */
.driver = {
.name= "xxxfb",
},
};
static struct platform_device *xxxfb_device;
#ifndef MODULE
/*
* Setup
*/
/*
* Only necessary if your driver takes special options,
* otherwise we fall back on the generic fb_setup().
*/
int __init xxxfb_setup(char *options)
{
/* Parse user speficied options (`video=xxxfb:') */
}
#endif /* MODULE */
static int __init xxxfb_init(void)
{
int ret;
/*
* For kernel boot options (in 'video=xxxfb:<options>' format)
*/
#ifndef MODULE
char *option = NULL;
if (fb_get_options("xxxfb", &option))
return -ENODEV;
xxxfb_setup(option);
#endif
ret = platform_driver_register(&xxxfb_driver);
if (!ret) {
xxxfb_device = platform_device_register_simple("xxxfb", 0,
NULL, 0);
if (IS_ERR(xxxfb_device)) {
platform_driver_unregister(&xxxfb_driver);
ret = PTR_ERR(xxxfb_device);
}
}
return ret;
}
static void __exit xxxfb_exit(void)
{
platform_device_unregister(xxxfb_device);
platform_driver_unregister(&xxxfb_driver);
}
#endif/*CONFIG_PCI*/
/* ------------------------------------------------------------------------- */
/*
* Modularization
*/
module_init(xxxfb_init);
module_exit(xxxfb_remove);
MODULE_LICENSE("GPL");

每日一道理
美丽是平凡的，平凡得让你感觉不到她的存在；美丽是平淡的，平淡得只剩下温馨的回忆；美丽又是平静的，平静得只有你费尽心思才能激起她的涟漪。

这里就开始渐渐啃一啃这个硬骨架吧

毫无疑问，先找到module_init(xxxfb_init)，xxxfb_init这个方式是这个驱动的入口，我们要找到这个法方，代码中我已经标注出来，原来在这个构架中采用了两种法方来实现framebuffer驱动，分别是pci子系统方式和platform子系统方式，这里他们的实现法方基本相似，只是在匹配device时有所不同，我们没有必要过于关注这里，大家也可以看到，他们的proble法方是一样的，这个proble才是我们要真正好好析分的

第一件事就是为fb_info动态申请内存空间，很有必要析分一下这个法方

/**
* framebuffer_alloc - creates a new frame buffer info structure
*
* @size: size of driver private data, can be zero
* @dev: pointer to the device for this fb, this can be NULL
*
*Creates a new frame buffer info structure.Also reserves @size bytes
* fordriverprivatedata(info->par).info->par(ifany)will be
*alignedtosizeof(long).
*
* Returns the new structure, or NULL if an error occured.
*
*/
struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
{
#define BYTES_PER_LONG (BITS_PER_LONG/8)
#define PADDING (BYTES_PER_LONG - (sizeof(struct fb_info) % BYTES_PER_LONG))
int fb_info_size = sizeof(struct fb_info);
struct fb_info *info;
char *p;
if (size)
fb_info_size += PADDING;
p = kzalloc(fb_info_size + size, GFP_KERNEL);
if (!p)
return NULL;
info = (struct fb_info *) p;
if (size)
info->par = p + fb_info_size;
info->device = dev;
#ifdef CONFIG_FB_BACKLIGHT
mutex_init(&info->bl_curve_mutex);
#endif
return info;
#undef PADDING
#undef BYTES_PER_LONG
}

其实这里注释也已经说清楚了，这个法方不止为fb_info申请了内存空间，还为fb_info中的一个void型指针par分配了内存空间，这个par将会保存之后在这个驱动中的私有变量，是一个结构，保存了很多driver的相关信息，保存到par中，之后想要使用的时候就很容易得到

这个构架中的其他法方都没有实现，他们就是访问driver时候体具的处理函数，就是要我们要去花大力气去做的事情

之后在真正的framebuffer驱动程序中再去好好析分这些法方吧

待续。。。。。。

文章结束给大家分享下程序员的一些笑话语录： 打赌
飞机上，一位工程师和一位程序员坐在一起。程序员问工程师是否乐意和他一起玩一种有趣的游戏。工程师想睡觉，于是他很有礼貌地拒绝了，转身要睡觉。程序员坚持要玩并解释说这是一个非常有趣的游戏："我问你一个问题，如果你不知道答案，我付你5美元。然后你问我一个问题，如果我答不上来，我付你5美元。"然而，工程师又很有礼貌地拒绝了，又要去睡觉。　　程序员这时有些着急了，他说："好吧，如果你不知道答案，你付5美元；如果我不知道答案，我付50美元。"果然，这的确起了作用，工程师答应了。程序员就问："从地球到月球有多远？"工程师一句话也没有说，给了程序员5美元。　　现在轮到工程师了，他问程序员："什么上山时有三条腿，下山却有四条腿？"程序员很吃惊地看着工程师，拿出他的便携式电脑，查找里面的资料，过了半个小时，他叫醒工程师并给了工程师50美元。工程师很礼貌地接过钱又要去睡觉。程序员有些恼怒，问："那么答案是什么呢？"工程师什么也没有说，掏出钱包，拿出5美元给程序员，转身就去睡觉了。