详解linux驱动编写（sd卡驱动）

详解linux驱动编写（sd卡驱动）
随着sd卡的流⾏，sd卡在嵌⼊式设备上使⽤的场景也越来越多。

那下⾯我们可以看⼀下，linux驱动框架上是怎么处理sd卡驱动的？
1、代码⽬录地址
drivers/mmc
2、基本结构
从mmc的代码结构可以看得出，主要分为两个部分，其中core为协议部分，host为各个soc的适配部分
host是我们需要真正关⼼的代码
3、以s3c为例，观察makefile
obj-$(CONFIG_MMC_SDHCI_S3C) += sdhci-s3c.o
......
obj-$(CONFIG_MMC_S3C) += s3cmci.o
4、根据s3c阅读Kconfig，确认s3c下的sd卡还依赖哪些⽂件
config MMC_SDHCI_S3C
tristate "SDHCI support on Samsung S3C SoC"
depends on MMC_SDHCI && PLAT_SAMSUNG
help
This selects the Secure Digital Host Controller Interface (SDHCI)
often referrered to as the HSMMC block in some of the Samsung S3C
range of SoC.
If you have a controller with this interface, say Y or M here.
If unsure, say N.
config MMC_SDHCI_S3C_DMA
bool "DMA support on S3C SDHCI"
depends on MMC_SDHCI_S3C
help
Enable DMA support on the Samsung S3C SDHCI glue. The DMA
has proved to be problematic if the controller encounters
certain errors, and thus should be treated with care.
YMMV.
config MMC_S3C
tristate "Samsung S3C SD/MMC Card Interface support"
depends on ARCH_S3C24XX
depends on S3C24XX_DMAC
help
This selects a driver for the MCI interface found in
Samsung's S3C2410, S3C2412, S3C2440, S3C2442 CPUs.
If you have a board based on one of those and a MMC/SD
slot, say Y or M here.
If unsure, say N.
5、MMC_S3C和MMC_SDHCI_S3C是主要的macro，接着了解两个macro对应⽂件的数据结构
⾸先看⼀下s3cmci.c⽂件，
static const struct mmc_host_ops s3cmci_ops = {
.request = s3cmci_request,
.set_ios = s3cmci_set_ios,
.get_ro = mmc_gpio_get_ro,
.get_cd = mmc_gpio_get_cd,
.enable_sdio_irq = s3cmci_enable_sdio_irq,
};
再看⼀下sdhci-s3c.c⽂件，
static struct sdhci_ops sdhci_s3c_ops = {
.get_max_clock = sdhci_s3c_get_max_clk,
.set_clock = sdhci_s3c_set_clock,
.get_min_clock = sdhci_s3c_get_min_clock,
.set_bus_width = sdhci_set_bus_width,
.reset = sdhci_reset,
.set_uhs_signaling = sdhci_set_uhs_signaling,
};
6 、从host⾓度来说，有了platform driver和上⾯的host driver，驱动流程就算搞清楚了。

但是如果深⼊下去的话，还是需要好好读⼀下sd协议，这⾥⾯花的时间最多。

以上就是本⽂的全部内容，希望对⼤家的学习有所帮助，也希望⼤家多多⽀持。