mmc: block: Add new ioctl to send multi commands

Certain eMMC devices allow vendor specific device information to be read
via a sequence of vendor commands. These vendor commands must be issued
in sequence and an atomic fashion. One way to support this would be to
add an ioctl function for sending a sequence of commands to the device
atomically as proposed here. These multi commands are simple array of
the existing mmc_ioc_cmd structure.

The structure passed via the ioctl uses a __u64 type to specify the number
of commands (so that the structure is aligned on a 64-bit boundary) and a
zero length array as a header for list of commands to be issued. The
maximum number of commands that can be sent is determined by
MMC_IOC_MAX_CMDS (which defaults to 255 and should be more than
sufficient).

This based upon work by Seshagiri Holi <sholi@nvidia.com>.

Signed-off-by: Seshagiri Holi <sholi@nvidia.com>
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 18 insertions, 1 deletions

diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h
index 1f5e68923929..7e385b83b9d8 100644
--- a/include/uapi/linux/mmc/ioctl.h
+++ b/include/uapi/linux/mmc/ioctl.h
@@ -45,8 +45,24 @@ struct mmc_ioc_cmd {
 };
 #define mmc_ioc_cmd_set_data(ic, ptr) ic.data_ptr = (__u64)(unsigned long) ptr
 
-#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
+/**
+ * struct mmc_ioc_multi_cmd - multi command information
+ * @num_of_cmds: Number of commands to send. Must be equal to or less than
+ *	MMC_IOC_MAX_CMDS.
+ * @cmds: Array of commands with length equal to 'num_of_cmds'
+ */
+struct mmc_ioc_multi_cmd {
+	__u64 num_of_cmds;
+	struct mmc_ioc_cmd cmds[0];
+};
 
+#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
+/*
+ * MMC_IOC_MULTI_CMD: Used to send an array of MMC commands described by
+ *	the structure mmc_ioc_multi_cmd. The MMC driver will issue all
+ *	commands in array in sequence to card.
+ */
+#define MMC_IOC_MULTI_CMD _IOWR(MMC_BLOCK_MAJOR, 1, struct mmc_ioc_multi_cmd)
 /*
  * Since this ioctl is only meant to enhance (and not replace) normal access
  * to the mmc bus device, an upper data transfer limit of MMC_IOC_MAX_BYTES
@@ -54,4 +70,5 @@ struct mmc_ioc_cmd {
  * block device operations.
  */
 #define MMC_IOC_MAX_BYTES  (512L * 256)
+#define MMC_IOC_MAX_CMDS    255
 #endif /* LINUX_MMC_IOCTL_H */