saa711x驱动分析.doc

Saa7115的驱动支持saa7111, saa7111a, saa7113, saa7114,saa7115 and saa7118.这里分析的代码是来自linux-2.6.19内核。具体路径为/driver/media/video/saa7115.c。1. 模块的加载与卸载module_init(saa711x_init_module);module_exit(saa711x_cleanup_module);static int _init saa711x_init_module(void) return i2c_add_driver(&i2c_driver_saa711x);static void _exit saa711x_cleanup_module(void) i2c_del_driver(&i2c_driver_saa711x);i2c_add_driver()用于注册设备驱动程序的i2c_driver数据结构。i2c_del_driver()则相反，用于注销设备驱动程序的i2c_driver树结构。由此加载i2c_driver的结构体i2c_driver_saa711xstatic struct i2c_driver i2c_driver_saa711x = .driver = .name = saa7115, , .id = I2C_DRIVERID_SAA711X, .attach_adapter = saa711x_probe, .detach_client = saa711x_detach, .command = saa711x_command,;其中driver为驱动名。id为驱动号。attach_adapter依附i2c_adapter函数指针。detach_client为脱离i2c_client函数指针。command为实现针对设备的控制命令指针，类似ioctl。下面分别对saa711x_probe(),saa711x_detach(),saa711x_command()作分析。2. saa711x_probe()函数saa711x_probe()是实现attach_adapter的函数。可以简单的通过调用i2c_probe()函数来实现。static int saa711x_probe(struct i2c_adapter *adapter) if (adapter-class & I2C_CLASS_TV_ANALOG | adapter-class & I2C_CLASS_TV_DIGITAL) return i2c_probe(adapter, &addr_data, &saa711x_attach); return 0;adapter：内核指针数组adapters的一个元素，代表当前被扫描的i2c 总线。addr_data：在ltc3445.h中由I2C_CLIENT_INSMOD宏创建的静态二维数组，表示使用该驱动程序的所有设备的所有可能地址的集合。saa711x_attach：为一个在地址成功检测时被调用的回调函数，用于创建描述该设备的i2c_client数据结构并初始化。i2c_probe 函数用于认领adapter所指适配器上的所有合适的设备。设备可能使用的地址的“线索”由addr_data二元数组指出，如果检测到存在实际设备，则调用saa711x_attach回调函数分配、初始化设备的i2c_client等数据结构。由此引出了函数saa7111x_attach():static int saa711x_attach(struct i2c_adapter *adapter, int address, int kind);adapter：i2c_adapter类型的适配器 address：chip address。下面分析该函数的代码:struct i2c_client *client; /具体设备名struct saa711x_state *state; /saa711x_state结构体/*saa711x_state的结构体如下:struct saa711x_state v4l2_std_id std; int input; int output; int enable; int radio; int bright; int contrast; int hue; int sat; int width; int height; u32 ident; u32 audclk_freq; u32 crystal_freq; u8 ucgc; u8 cgcdiv; u8 apll;*/if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA) return 0;这里调用了函数i2c_check_functionality()判断指定适配器是否支持相应的方法。I2C_FUNC_SMBUS_BYTE_DATA: Handles the SMBUS read_byte_data and write_byte_data commands.接着是对i2c_client初始化，初始化的过程中用到了saa711x_write和saa711x_read两个函数。l saa711x_write():static inline int saa711x_write(struct i2c_client *client, u8 reg, u8 value) return i2c_smbus_write_byte_data(client, reg, value);这个函数的功能是把value的值写到client设备的reg寄存器中。它通过调用i2c_smbus_write_byte_data来实现。s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value) union i2c_smbus_data data; data.byte = value; return i2c_smbus_xfer(client-adapter,client-addr,client-flags, I2C_SMBUS_WRITE,command, I2C_SMBUS_BYTE_DATA,&data);EXPORT_SYMBOL(i2c_smbus_write_byte_data);可以看出实际上是调用i2c_smbus_xfer()来实现。这个函数通过适配器驱动提供的总线访问方法(i2c_algorithm的smbus_xfer方法)尝试访问处于addr地址上的设备。s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags, char read_write, u8 command, int size, union i2c_smbus_data * data) s32 res; flags &= I2C_M_TEN | I2C_CLIENT_PEC; if (adapter-algo-smbus_xfer) mutex_lock(&adapter-bus_lock); res = adapter-algo-smbus_xfer(adapter,addr,flags,read_write, command,size,data); mutex_unlock(&adapter-bus_lock); else res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write, command,size,data); return res;而目前i2c中没有实现smbus_xfer方法而只实现了master_xfer方法，所以相关的操作就由i2c_smbus_xfer_emulated函数来模拟。这个函数比较长，所以只分析它的参数。其中size为I2C_SMBUS_QUICK的一段。第二个参数为需要检测的设备地址，第四个参数read_write为0，表示进行写入操作。如果使用这个总线地址和设备通信成功，则说明设备使用的正是这个地址。l saa711x_read():static inline int saa711x_read(struct i2c_client *client, u8 reg) return i2c_smbus_read_byte_data(client, reg);这个函数的功能是把client设备的reg寄存器中的值读出并返回。它通过调用i2c_smbus_read_byte_data来实现。s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command) union i2c_smbus_data data; if (i2c_smbus_xfer(client-adapter,client-addr,client-flags, I2C_SMBUS_READ,command, I2C_SMBUS_BYTE_DATA,&data) return -1; else return data.byte;EXPORT_SYMBOL(i2c_smbus_read_byte_data);可以看出，它也是调用i2c_smbus_xfer函数来实现的，因此和saa711x_write()的过程基本一样。再回头看i2c_client的初始化：分配i2c_client的内存空间 client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL); if (client = 0) return -ENOMEM;初始化client的addr,adapter和driver。没什么可说的。 client-addr = address; client-adapter = adapter; client-driver = &i2c_driver_saa711x;初始化client的name。 snprintf(client-name, sizeof(client-name) - 1, saa7115); for (i = 0; i 9) namei += a - 9 - 1; namei = 0;查看芯片号是否为saa711x。 saa711x_write(client, 0, 5); chip_id = saa711x_read(client, 0) & 0x0f; /* Check whether this chip is part of the saa711x series */ if (memcmp(name, 1f711, 5) v4l_dbg(1, debug, client, chip found 0x%x (ID %s) does not match a known saa711x chip.n, address name, sizeof(client-name) - 1, saa711%d,chip_id); v4l_info(client, saa711%d found (%s) 0x%x (%s)n, chip_id, name, address name);到此，i2c_client结构体client初始化完毕。下面开始对saa711x_state结构体state进行初始化。 state = kzalloc(sizeof(struct saa711x_state), GFP_KERNEL); i2c_set_clientdata(client, state);/将state存到client-dev中 if (state = NULL) kfree(client); return -ENOMEM; state-input = -1; state-output = SAA7115_IPORT_ON; state-enable = 1; state-radio = 0; state-bright = 128; state-contrast = 64; state-hue = 0; state-sat = 64;然后根据芯片号确认是哪款芯片。并选择不同的初始化函数。 switch (chip_id) case 1: state-ident = V4L2_IDENT_SAA7111; break; case 3: state-ident = V4L2_IDENT_SAA7113; break; case 4: state-ident = V4L2_IDENT_SAA7114; break; case 5: state-ident = V4L2_IDENT_SAA7115; break; case 8: state-ident = V4L2_IDENT_SAA7118; break; default: state-ident = V4L2_IDENT_SAA7111; v4l_info(client, WARNING: Chip is not known - Falling back to saa7111n); state-audclk_freq = 48000; v4l_dbg(1, debug, client, writing init valuesn); /* init to 60hz/48khz */ state-crystal_freq = SAA7115_FREQ_24_576_MHZ; switch (state-ident) case V4L2_IDENT_SAA7111: saa711x_writeregs(client, saa7111_init); break; case V4L2_IDENT_SAA7113: saa711x_writeregs(client, saa7113_init); break; default: state-crystal_freq = SAA7115_FREQ_32_11_MHZ; saa711x_writeregs(client, saa7115_init_auto_input); 以7111的初始化函数saa7111_init()为例分析芯片的初始化。这里用到了saa711x_writeregs()函数。在saa711x_writeregs()中又调用了i2c_get_clientdata()，saa711x_has_reg()以及saa711x_write()。saa711x_write()在前面已经分析过了，这里重点分析i2c_getclientdata()和saa711x_has_reg()。l i2c_get_clientdata()是i2c的一个API。static inline void *i2c_get_clientdata (struct i2c_client *dev) return dev_get_drvdata (&dev-dev);static inline void *dev_get_drvdata (struct device *dev) return dev-driver_data;很明显，是将一个i2c_client结构体中的dev-driver_data返回。l saa711x_has_reg()函数/* Sanity routine to check if a register is present */static int saa711x_has_reg(const int id, const u8 reg) if (id = V4L2_IDENT_SAA7111) return reg 0x20 & reg != 0x01 & reg != 0x0f & (reg 0x19) & reg != 0x1d & reg != 0x1e; /* common for saa7113/4/5/8 */ if (unlikely(reg = 0x3b & reg = 0xb5 & reg = 0xe5 & reg = 0x89 & reg = 0x8e) return 0; switch (id) case V4L2_IDENT_SAA7113: return reg != 0x14 & (reg 0x1e) & (reg 0x3f) & reg != 0x5d & reg 0x63; case V4L2_IDENT_SAA7114: return (reg 0x1e) & (reg 0x2f) & (reg 0x7f) & reg != 0x33 & reg != 0x37 & reg != 0x81 & reg 0xf0; case V4L2_IDENT_SAA7115: return (reg 0x2f) & reg != 0x65 & (reg 0xfe); case V4L2_IDENT_SAA7118: return (reg 0x1d) & (reg 0x22) & (reg 0x28) & reg != 0x33 & reg != 0x37 & (reg 0x7f) & reg != 0x81 & reg ident,reg) if (saa711x_write(client, reg, data) std) return; state-std = std; / This works for NTSC-M, SECAM-L and the 50Hz PAL variants. if (std & V4L2_STD_525_60) v4l_dbg(1, debug, client, decoder set standard 60 Hzn); saa711x_writeregs(client, saa7115_cfg_60hz_video); saa711x_set_size(client, 720, 480); else v4l_dbg(1, debug, client, decoder set standard 50 Hzn); saa711x_writeregs(client, saa7115_cfg_50hz_video); saa711x_set_size(client, 720, 576); /* Register 0E - Bits D6-D4 on NO-AUTO mode (SAA7111 and SAA7113 doesnt have auto mode) 50 Hz / 625 lines 60 Hz / 525 lines 000 PAL BGDHI (4.43Mhz) NTSC M (3.58MHz) 001 NTSC 4.43 (50 Hz) PAL 4.43 (60 Hz) 010 Combination-PAL N (3.58MHz) NTSC 4.43 (60 Hz) 011 NTSC N (3.58MHz) PAL M (3.58MHz) 100 reserved NTSC-Japan (3.58MHz) */ if (state-ident = V4L2_IDENT_SAA7111 | state-ident = V4L2_IDENT_SAA7113) u8 reg = saa711x_read(client, R_0E_CHROMA_CNTL_1) & 0x8f; if (std = V4L2_STD_PAL_M) reg |= 0x30; else if (std = V4L2_STD_PAL_N) reg |= 0x20; else if (std = V4L2_STD_PAL_60) reg |= 0x10; else if (std = V4L2_STD_NTSC_M_JP) reg |= 0x40; else if (std & V4L2_STD_SECAM) reg |= 0x50; saa711x_write(client, R_0E_CHROMA_CNTL_1, reg); e