1、*/*/* 2007.6.18*在/kernel/include/asm-arm/arch-s3c2410/bitfield.h 文件中：#ifndef _ASSEMBLY_#define UData(Data) (unsigned long) (Data)#else#define UData(Data) (Data)#endif例：UData(5); = 5/* MACRO: Fld*PurposeThe macro Fld encodes a bit field, given its siz( and its shift valuewith respect to bit 0.*NoteA

2、more intuitive way to encode bit fields would ha、 been to use theirmask. However, extracting size and shift value information from a bitfields mask is cumbersome and might break the assembler (255-characterline-size limit).*InputSizeSize of the bit field, in number of bitShftShift value of the bitfi

3、eld with respectto bit 0.*OutputFldEncoded bit field.*/#define Fld(Size, Shft) (Size) 16)例：FSize(0 x20005);#define FShft(Field)(Field)& 0 x0000FFFF)例：FShft(0 x20005);/* MACRO: FInsrt* Purpose* The macro FInsrt inserts a value into a bit fiel by shifting the* former appropriately.* Input*ValueBit-fie

4、ld value.*FieldEncoded bit field (using the macro Fld)*Output*FInsrtBit-field value positionedappropriately.*/#define FInsrt(Value, Field) (UData (Value) FShft (Field)例：FInsrt(0 x3, 0 x20005); = 0 x3 fb.fix.smem_len = fbi-max_xres * fbi-max_yres * fbi-max_bpp / 8;fbi-map_size = PAGE_ALIGN(fbi-fb.fix

5、.smem_len + PAGE_SIZE);fbi-map_cpu = consistent_alloc(GFP_KERNEL,fbi-map_size,&fbi-map_dma);if (fbi-map_cpu)(fbi-screen_cpu = fbi-map_cpu + PAGE_SIZE;fbi-screen_dma = fbi-map_dma + PAGE_SIZE;fbi-fb.fix.smem_start = fbi-screen_dma;在/kernel/include/asm-arm/proc-armo/page.h 文件中：/* PAGE_SHIFT determines

6、 the page size. This is configurable. */#if defined(CONFIG_PAGESIZE_16)#define PAGE_SHIFT 14 /* 16K */#else /* default */#define PAGE_SHIFT 15 /* 32K */#endif在/kernel/include/asm-arm/page.h 文件中：#define PAGE_SIZE(1UL fb.fix.smem_len = 240*320*16/8 = 0 x25800 =150K(9.375 個 PAGE)PAGE_SHIFT = 14PAGE_SIZ

7、E = 1map_size = PAGE_ALIGN(fbi-fb.fix.smem_len +PAGE_SIZE) = PAGE_ALIGN(150K + 16K) = PAGE_ALIGN(166K)=(166K + 16K - 1) & 0 xFFFFC000 = 0 x2D7FF & 0 xFFFFC000 : 0 x2C000 =176Kconsistent_alloc(GFP_KERNEL, 176K, &fbi-map_dma);最后得到：framebuffer (物理地址) TOC o 1-5 h z I1I.I11map_dmaI16K|分配了 |1screen_dma =f

8、bi-fb.fix.smem_start176K |共 11 個 | 160K = 10個 PAGEPAGE |160K |可以容下所需的150K視頻緩沖區大小(16K) |11|. |1*/* 2007.6.19*/*在/kernel/drivers/video/s3c2410fb.c 文件中的 s3c2410fb_activate_var 函數中：unsigned long VideoPhysicalTemp = fbi-screen_dma;這里已經得到了 framebuffer在內存中的起始地址為 VideoPhysicalTemp,地址數據位為 A30:0。 I 4 n *I I 4

9、 c 2. cr 4 mi j I rnew_regs.lcdcon1 - fbi-reg.lcdcon1 & LCD1_ENVID;new_regs.lcdcon2 - (fbi-reg.lcdcon2 & LCD2_LINEVAL_MSK)| LCD2_LINEVAL(var-yres - 1);/* TFT LCD only ! */new_regs.lcdcon3 - (fbi-reg.lcdcon3 & LCD3_HOZVAL_MSK)| LCD3_HOZVAL(var-xres - 1);new_regs.lcdcon4 - fbi-reg.lcdcon4;new_regs.lcd

10、con5 - fbi-reg.lcdcon5;LCDCON1首先需要禁止視頻輸出才能進行寄存器的設置，然后 對LCDCON2，LCDCON3進行設置，主要是增加LINEVAL和HOZVAL這 兩個顯示尺寸的參數。LCDCON4，LCDCON5按原來配置設置。LCDBANK29:21為系統內存中視頻緩沖區在系統存儲器內的段地址的A30:22LCDBASEU20:0 為 LCD framebuffer 的起始地址的 A21:1LCDBASEL20:0 為 LCD framebuffer 的結束地址的 A21:1OFFSIZE21:11為某一行的第一個半字與前一行最后一個半字 之間的距離(單位：半字

11、數，即2個字節)PAGEWIDTH10:0為顯示存儲區的可見幀寬度(單位：半字數， 即2個字節)new_regs.lcdsaddr1 =LCDADDR_BANK(unsigned long)VideoPhysicalTemp 22)| LCDADDR_BASEU(unsigned long)VideoPhysicalTemp 1);new_regs.lcdsaddr2 = LCDADDR_BASEL(unsigned long)VideoPhysicalTemp + (var-xres * 2 * (varyres) 1);這里LCDADDR_BASEL的計算方法為用framebuffer在內

12、存 中的起始地址VideoPhysicalTemp，加上framebuffer的大小(LCD 屏的寬度* LCD屏的高度*每像素的位數/每字節的位數)，得到 framebuffer在內存中的結束地址，然后右移1位。new_regs.lcdsaddr3 = LCDADDR_OFFSET(0) |(LCDADDR_PAGE(var-xres);這里PAGEWIDTH的計算方法為：LCD屏的寬度*每像素的位數 /16位(半字)。問題：以上這些操作是否已經對DMA控制器進行了設置？我認為這里將framebuffer在內存中的起始地址為 VideoPhysicalTemp 變換后載入 LCDADDR1，

13、LCDADDR2，LCDADDR3 中 就已經完成了對LCDCDMA控制器的源數據的基地址設置，當打開 LCDCON1 |= LCD1_ENVID;后就可以由LCDCDMA控制器自動從 framebuffer中傳數據到LCD屏幕了。在/kernel/drivers/video/s3c2410fb.c 文件中的 xxx_stn_info 結構體初始化中：lcdcon5 : LCD5_FRM565 | LCD5_INVVLINE | LCD5_INVVFRAME | LCD5_HWSWP | LCD5_PWREN,INVVCLK， INVLINE， INVFRAME， INVVD :通過前面的 時

14、序圖，我們知道，CPU的LCD控制器輸出的時序默認是正脈沖，而 LCD 需要 VSYNC(VFRAME)、VLINE(HSYNC)均為負脈沖，因此 INVLINE 和INVFRAME必須設為“1 ”，即選擇反相輸出。INVVDENINVPWREN， INVLEND的功能同前面的類似。PWREN為LCD電源使能控制。在CPU LCD控制器的輸出信號 中，有一個電源使能管腳LCD_PWREN,用來做為LCD屏電源的開關信 號。其中LCD5_HWSWP 一項，設置了 LCD從內存中顯示數據時， 經過了半字交換。16BPP Display(BSWP = 0, HWSWP = 0)D31:16D15:0

15、 TOC o 1-5 h z 000HP1P2004HP3P4008HP5P6(BSWP = 0, HWSWP = 1)D31:16 D15:0000H P2P1004H P4P3008H P6 P5像素顯示順序如下：P1 P2 P3 P4 P5 .例如：內存地址的數據為：0 x11223344 （32位）系統存儲器采用Big-Endian （大端模式）存儲格式，地址數 據格式如下：D31:16 D15:00001020300H0 x11 0 x22 0 x33 0 x44（0 x1122）（0 x3344）04H .08H .則首先顯示0 x3344的數據到第一個像素，然后再顯示0 x112

16、2到 第二個像素。系統存儲器采用Little-Endian（小端模式）存儲格式，地 址數據格式如下：D31:16 D15:00302010000H0 x11 0 x22 0 x33 0 x44(0 x1122)(0 x3344)04H .08H .則首先顯示0 x3344的數據到第一個像素，然后再顯示0 x1122到 第二個像素。*/*/* 2007.6.20*/*在/kernel/arch/arm/mm/consistent.c 文件中的consistent_alloc 函數中：void *consistent_alloc(int gfp, size_t size, dma_addr_t*d

17、ma_handle)(virt = page_address(page);*dma_handle = virt_to_bus(virt);ret = _ioremap（virt_to_phys（virt）, size, 0）;這里調用該函數來分配一段內存空間有兩個返回值，一個返 回值返回給了 ret指針，另一個返回值返回給了 dma_handle指針。 virt_to_bus和virt_to_phys函數的調用可以參考下面的分析。經 過分析這兩個函數作用一樣，都是將virt這個虛擬地址轉換為物理 地址。所以返回給指針dma_handle的是所分配內存的起始地址（物 理地址）。_ioremap函

18、數的調用也可以參考下面的說明，該函數也 返回所分配內存的起始地址（虛擬地址），不過是經過I/O內存映射 的，把物理地址轉換為了虛擬地址。這樣一來就很清楚了，返回的framebuffer的物理地址給了 指針 dma_handle，也就是 fbi-map_dma，到 fbi-screen_dma，再 到 fbi-fb.fix.smem_start，最后到了指針 VideoPhysicalTemp，這 樣寫入到LCDADDR1，LCDADDR2寄存器中的framebuffer的地址其實 都是物理地址。而返回的framebuffer的虛擬地址給了指針ret，也就是 fbi-map_cpu，至lj fb

19、i-screen_cpu，最后到了 display-screen_base（見/kernel/drivers/video/s3c2410fb.c 文 件中的 s3c2410fb_set_var 函數）。在/kernel/drivers/video/fbmem.c 文件中：/*register_framebuffer - registers a frame buffer devicfb_info: frame buffer info structure*Registers a frame buffer device fb_info.*Returns negative errno on error

20、, or zero for success.*/intregister_framebuffer(struct fb_info *fb_info)/*unregister_framebuffer - releases a frame buffer devicefb_info: frame buffer info structure*Unregisters a frame buffer device fb_info.* Returns negative errno on error, or zero for success.*/intunregister_framebuffer(struct fb

21、_info *fb_info)static intfb_open(struct inode *inode, struct file *file)static intfb_release(struct inode *inode, struct file *file)static ssize_tfb_read(struct file *file, char *buf, size_t count, loff_t *ppos)static ssize_tfb_write(struct file *file, const char *buf, size_t count, loff_t *ppos)sta

22、tic intfb_ioctl(struct inode *inode, struct file *file, unsignedint cmd,unsigned long arg)static intfb_mmap(struct file *file, struct vm_area_struct * vma)在該文件中包含了所有驅動LCD的函數。在fb_read和 fb_write這兩個函數中，都對framebuffer進行了操作。fb_read函數中：char *base_addr;base_addr = info-disp-screen_base;count -= copy_to_user

23、(buf, base_addr+p, count);fb_write函數中：char *base_addr;base_addr = info-disp-screen_base;count -= copy_from_user(base_addr+p, buf, count);所讀寫的framebuffer的基地址就是disp-screen_base，也就 是fbi-screen_cpu所指的framebuffer的虛擬地址。從而得到：framebuffer (虛擬地址) TOC o 1-5 h z |1|.|map_cpuI16K|分配了 |1screen_cpu =display-screen

24、_base176K |共 11 個 | 160K = 10個 PAGEPAGE |160K |可以容下所需的150K視頻緩沖區大小(16K) |11|. |1其中 display-screen_base 結構在/kernel/include/video/fbcon.h 文件中定義。得出結論，在分配framebuffer時一共返回兩個指針，雖然 是同一塊內存空間，但一個返回的是實際的物理地址，另一個返回的 是經過地址轉換的虛擬地址。在設置LCD控制器中framebuffer起 始地址寄存器時，用的是所分配內存的物理地址；而當要對 framebuffer進行讀寫操作時，用的是同一塊內存的物理地址所

25、轉換 后的虛擬地址。由此可以知道，內核在對每個I/O地址進行讀寫操 作時用的都是經過轉換的虛擬地址。在/kernel/include/asm-arm/arch-s3c2410/memory.h 文件中：/*Page offset: 3GB*/#define PAGE_OFFSET (0 xc0000000UL)#define PHYS_OFFSET (0 x30000000UL)/*We take advantage of the fact that physical and virtu address can be thesaem. Thu NUMA code is handling the

26、 large holes that might exist between* all memory banks.*/ #define _virt_to_phys_is_a_macro #define _phys_to_virt_is_a_macro#define_virt_to_phys(x) (x) - PAGE_OFFSET + PHYS_OFFSET)#define_phys_to_virt(x) (x) - PHYS_OFFSET + PAGE_OFFSET)由此可見：起始點地址PHYS_OFFSET TOC o 1-5 h z PAGE_OFFSET |-0 x30000000-|間

27、隔1PHYS_OFFSET (物理地址起始點)： |1| |0 xc00000001PAGE_OFFSET (虛擬地址起始點)： |1物理地址與虛擬地址的間隔為：PAGE_OFFSET - PHYS_OFFSET。這樣一來，以上對物理地址和虛擬地址之間轉換的宏定義就很好理解 了。虛擬地址轉為物理地址宏：_virt_to_phys(x)=(x) - (PAGE_OFFSET - PHYS_OFFSET) = (x) - PAGE_OFFSET PHYS_OFFSET物理地址轉為虛擬地址宏：_phys_to_virt(x)=(x) + (PAGE_OFFSET - PHYS_OFFSET) = (

28、x) + PAGE_OFFSET PHYS_OFFSET內核虛擬地址和實際物理地址僅僅是相差一個偏移量(PAGE_OFFSET),可以很方便的將其轉化為物理內存地址，同時內核 也提供了 virt_to_phys()函數將內核虛擬空間中的物理影射區地址 轉化為物理地址。/*Virtual view DMA view memory address translationsvirt_to_bus: Used to translate the virtual address to anaddress suitable to be passed to set_dma_addrbus_to_virt: U

29、sed to convert an address for DMA operationsto an address that the kernel can use.*/#define _virt_to_bus_is_a_macro#define _bus_to_virt_is_a_macro#define _virt_to_bus(x) _virt_to_phys(x)#define _bus_to_virt(x) _phys_to_virt(x)這里注意：virt_to_bus(x)就等于_virt_to_phys(x)在/kernel/include/asm-arm/memory.h 文件

30、中：/*These are *only* valid on the kernel direct mapped RA memory.*/static inline unsigned long virt_to_phys(volatile void *x)(return _virt_to_phys(unsigned long)(x);/*Virtual DMA view memory address translationsAgain, these are *only* valid on the kernel direct mapped RAMmemory.*/#define virt_to_bus

31、(x)(_virt_to_bus(unsignedlong)(x)由上面的分析可知：virt_to_bus(x)和 virt_to_phys(volatile void *x)這兩個函數調用的都是 _virt_to_phys(x)即(x) - PAGE_OFFSET + PHYS_OFFSET)。所以 這兩個調用都是將虛擬地址轉換為了物理地址。在/kernel/arch/arm/mm/ioremap.c 文件中：/*Remap an arbitrary physical address space into the kernel virtualaddress space. Needed whe

32、n the kernel wants to access high addressesdirectly.*NOTE! We need to allow nonaligned mappings too: we will obviouslyhave to convert them into an offset in a aligned mapping, but thecaller shouldnt need to know that small detail.*flags are the extra L_PTE_ flags that you wan to specify for thismapp

33、ing. See include/asm-arm/proc-armv/pgtable.h for more information.*/void * _ioremap(unsigned long phys_addr, size_t size, unsigned long flags)ioremap函數的作用是將physical address以及bus address 映射為 kernel 的virtual adrress。ioremap的作用是把I/O內存地址（物理地址）映射到虛擬 地址空間，使用之前需要分配I/O內存區域。但是，ioremap函數 的內部實現并不是簡單的（IO的物理地址）-

34、0 x10000000 +0XE4000000）。所以，得到的虛擬地址可能是不同的。因為linux用的是頁面映射機制，CPU不能按物理地址來訪 問存儲空間，而必須使用虛擬地址，所以必須反向的從物理地址出發 找到一片虛存空間并建立起映射。*/* 2007.6.22/* /*在/kernel/drivers/video/fbmem.c 文件中：static struct file_operations fb_fops = owner: THIS_MODULE,read: fb_read,write: fb_write,ioctl: fb_ioctl,mmap: fb_mmap,open: fb_o

35、pen,release: fb_release,#ifdef HAVE_ARCH_FB_UNMAPPED_AREAget_unmapped_area: get_fb_unmapped_area,#endif;這個結構中定義了對LCD所分配的framebuffer進行讀寫操作， 以及一些內存映射之類的函數，這些源函數都在該文件中。/*register_framebuffer - registers a frame buffer devicfb_info: frame buffer info structure*Registers a frame buffer device fb_info.*Re

36、turns negative errno on error, or zero for success.*/intregister_framebuffer(struct fb_info *fb_info)這個是對LCD的framebuffer設備進行注冊時調用到的注冊函數，該函數在/kernel/drivers/video/s3c2410fb.c 文件的s3c2410fb_init函數里的最后部分被調用。fb_info-devfs_handle =devfs_register (devfs_handle, name_buf,DEVFS_FL_DEFAULT,FB_MAJOR, i, S_IFCH

37、R | S_IRUGO | S_IWUGO,&fb_fops, NULL);在注冊函數的最后部分，將前面的fb_fops結構里的各個驅動函 數的入口點傳入到devfs_register()設備注冊函數中。*/*/* 2007.6.26*/*上面這個devfs_register函數(原型在/kernel/fs/devfs/base.c 文件中)執行前，在fbmem_init 函數中 調用了函數：devfs_handle = devfs_mk_dir (NULL, fb”, NULL);在/kernel/fs/devfs/base.c 文件中：/*devfs_mk_dir - Create a d

38、irectory in the devfs namespace.dir: The handle to the parent devfs directory entry. If this is %NULL thenew name is relative to the root of the : The name of the : An arbitrary pointer which will be associated with the entry.*Use of this function is optional. The devfs_register(

39、 functionwill automatically create intermediate directories as needed. This functionis provided for efficiency reasons, as it provides a handle to a directory.Returns a handle which may later be used in a call to devfs_unregister().On failure %NULL is returned.*/devfs_handle_t devfs_mk_dir (devfs_ha

40、ndle_t dir, const char *name, void *info)這個devfs_mk_dir函數會在設備文件系統中創建一個名為 fb的目錄，并返回一個帶有devfs設備文件系統目錄結構的數據結 構變量devfs_handle。然后把這個數據結構作為下一步調用 devfs_register函數時的參數，該參數在調用設備文件系統注冊清 除函數devfs_unregister時也要作為參數傳入。/*devfs_register - Register a device entry.dir: The handle to the parent devfs directory entry. If th