SDIO驱动(14)card的CIS读取及解析

关于CIS需要清楚的：

1、CIS是什么

CIS-Card Information Structure的缩写，CIS的作用：

The CIS includes information on power, function, manufacturer and other things the hostneeds to determine if the I/O function(s) is appropriate to power-up.

2、CIS的呈现

CIS位于CIA区域,地址寻址范围0x001000~0x017FFF。CIS有两类：

(1)Common CIS，记录整张card的通用信息，比如厂商、VID等信息。

(2)Function CIS，每一个Function的特有信息。

一个CIS元素的组织结构：

它由结构体sdio_func_tuple表征:

/* * SDIO function CIS tuple (unknown to the core) */struct sdio_func_tuple {struct sdio_func_tuple *next;unsigned char code;unsigned char size;unsigned char data[0];};

这里总结下Function：Function代表card的一个具体功能，每一个card具有多个Function，Function的标号为0~7，特别地，0号针对的是CIA(可以简单理解就是用来访问CIA区域的)。在软件层面，Function由struct sdio_func表示，它作为一个device注册到系统中。

3、CIS的访问

需要两个条件：命令CMD52；CIS地址。

对于Common CIS，其地址保存在CCCR的0x09~0x0B地址处的寄存器中，3个寄存器值组成一个24位的地址。

对于Function CIS，其地址保存在每一个Function的FBR(Function Basic Registers)地址0x109-0x10B中。

软件层面，通过sdio_read_cis函数读取，函数原型：

static int sdio_read_cis(struct mmc_card *card, struct sdio_func *func)

如果参数func为NULL，访问的是Common CIS；否则则为指定Function的CIS。
4、CIS的解析

这正是接下来的重点要说的。

static int sdio_read_cis(struct mmc_card *card, struct sdio_func *func){int ret;struct sdio_func_tuple *this, **prev;unsigned i, ptr = 0;/* * Note that this works for the common CIS (function number 0) as * well as a function's CIS * since SDIO_CCCR_CIS and SDIO_FBR_CIS * have the same offset. */for (i = 0; i < 3; i++) {unsigned char x, fn;if (func)fn = func->num;elsefn = 0;ret = mmc_io_rw_direct(card, 0, 0,SDIO_FBR_BASE(fn) + SDIO_FBR_CIS + i, 0, &x);if (ret)return ret;ptr |= x << (i * 8);}if (func)prev = &func->tuples;elseprev = &card->tuples;BUG_ON(*prev);do {unsigned char tpl_code, tpl_link;ret = mmc_io_rw_direct(card, 0, 0, ptr++, 0, &tpl_code);if (ret)break;/* 0xff means we're done */if (tpl_code == 0xff)break;/* null entries have no link field or data */if (tpl_code == 0x00)continue;ret = mmc_io_rw_direct(card, 0, 0, ptr++, 0, &tpl_link);if (ret)break;/* a size of 0xff also means we're done */if (tpl_link == 0xff)break;this = kmalloc(sizeof(*this) + tpl_link, GFP_KERNEL);if (!this)return -ENOMEM;for (i = 0; i < tpl_link; i++) {ret = mmc_io_rw_direct(card, 0, 0,       ptr + i, 0, &this->data[i]);if (ret)break;}if (ret) {kfree(this);break;}/* Try to parse the CIS tuple */ret = cis_tpl_parse(card, func, "CIS",    cis_tpl_list, ARRAY_SIZE(cis_tpl_list),    tpl_code, this->data, tpl_link);if (ret == -EILSEQ || ret == -ENOENT) {/* * The tuple is unknown or known but not parsed. * Queue the tuple for the function driver. */this->next = NULL;this->code = tpl_code;this->size = tpl_link;*prev = this;prev = &this->next;if (ret == -ENOENT) {/* warn about unknown tuples */printk(KERN_WARNING "%s: queuing unknown"       " CIS tuple 0x%02x (%u bytes)\n",       mmc_hostname(card->host),       tpl_code, tpl_link);}/* keep on analyzing tuples */ret = 0;} else {/* * We don't need the tuple anymore if it was * successfully parsed by the SDIO core or if it is * not going to be queued for a driver. */kfree(this);}ptr += tpl_link;} while (!ret);/* * Link in all unknown tuples found in the common CIS so that * drivers don't have to go digging in two places. */if (func)*prev = card->tuples;return ret;}

12~25行，获取CIS的地址。保存信息的寄存器地址计算方式：SDIO_FBR_BASE(fn) + SDIO_FBR_CIS + i = fn * 0x100 + 0x09 + i，由于地址排列为little-endian格式(LSB first）所以依次左移拼成一个24位地址。
27~30行，之前说过，Common CIS是属于整张card的(30行)，而Function CIS是属于某个Function的(28行)。由于CIS信息都为设置，所以*prev指向的内容应该为NULL(32行)。

34~107行的代码段即是该函数的核心。结合上面提到的CIS的组织结构，当前ptr指向的一个CIS的code号码。

42行，code为0xFF标识一个CIS的结束。

46行，code为0x00标识当前元组(tuple)没什么内容，continue下一个tuple。

49行，当前ptr指向link域，标识当前tuple的数据size，同时也标识下一个tuple的偏移offset。

54行，link为0xFF同样标识一个CIS的结束。

57~70行，当前ptr指向数据区域的开始，读取数据；73~75行，解析数据：

static int cis_tpl_parse(struct mmc_card *card, struct sdio_func *func, const char *tpl_descr, const struct cis_tpl *tpl, int tpl_count, unsigned char code, const unsigned char *buf, unsigned size){int i, ret;/* look for a matching code in the table */for (i = 0; i < tpl_count; i++, tpl++) {if (tpl->code == code)break;}if (i < tpl_count) {if (size >= tpl->min_size) {if (tpl->parse)ret = tpl->parse(card, func, buf, size);elseret = -EILSEQ;/* known tuple, not parsed */} else {/* invalid tuple */ret = -EINVAL;}if (ret && ret != -EILSEQ && ret != -ENOENT) {printk(KERN_ERR "%s: bad %s tuple 0x%02x (%u bytes)\n",       mmc_hostname(card->host), tpl_descr, code, size);}} else {/* unknown tuple */ret = -ENOENT;}return ret;}

参数tpl、tpl_count为自己定义的一个cis_tpl类型数组及数组元素个数：

typedef int (tpl_parse_t)(struct mmc_card *, struct sdio_func *,   const unsigned char *, unsigned);struct cis_tpl {unsigned char code;unsigned char min_size;tpl_parse_t *parse;};/* Known TPL_CODEs table for CIS tuples */static const struct cis_tpl cis_tpl_list[] = {{0x15,3,cistpl_vers_1},{0x20,4,cistpl_manfid},{0x21,2,/* cistpl_funcid */},{0x22,0,cistpl_funce},};

cis_tpl的作用是，根据不同的code调用不同的数据解析函数parse。
cis_tpl_parse函数根据传参code进行比对，找出处理该code的解析函数，然后调用之完成解析。以code=20H为例，调用函数cistpl_manfid解析数据：

static int cistpl_manfid(struct mmc_card *card, struct sdio_func *func, const unsigned char *buf, unsigned size){unsigned int vendor, device;/* TPLMID_MANF */vendor = buf[0] | (buf[1] << 8);/* TPLMID_CARD */device = buf[2] | (buf[3] << 8);if (func) {func->vendor = vendor;func->device = device;} else {card->cis.vendor = vendor;card->cis.device = device;}return 0;}

返回到sdio_read_cis函数,76~104行如果解析成功(else分支)那么信息已经保存到相应的card或func中，所以可以释放掉之前malloc的内存；否则就把该信息保存到card或func的tuples指向的内存区域。

106行，ptr指向下一个tuple的code位置，开始下一轮读取、解析。

113、114行，把所有未知的tuple统一放到card的tuples里面。