Re: [RFC PATCH] mmc: block: Add new ioctl to send combo commands

[Ulf Hansson]

On 3 September 2015 at 17:08, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> Hi Olof,
>
> On 02/09/15 19:28, Olof Johansson wrote:
>> Hi,
>>
>> On Wed, Sep 2, 2015 at 7:21 AM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
>>> From: Seshagiri Holi <sholi@xxxxxxxxxx>
>>>
>>> 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 combo commands are simple array of
>>> the existing mmc_ioc_cmd structure.
>>
>> This seems reasonable to me, being able to do a sequence of
>> back-to-back operations without system read/writes slipping through.

I agree, this change seems reasonable!

Perhaps, from clarification point of view, we should change from
naming it "combo" commands to *sequence* of commands. Both in the code
and in the change log, please.

>>
>>> diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h
>>> index 1f5e68923929..5943e51f22b3 100644
>>> --- a/include/uapi/linux/mmc/ioctl.h
>>> +++ b/include/uapi/linux/mmc/ioctl.h
>>> @@ -45,8 +45,23 @@ 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_combo_cmd - combo command information
>>> + * @num_of_cmds: number of commands to send
>>> + * @mmc_ioc_cmd_list: pointer to list of commands
>>> + */
>>> +struct mmc_ioc_combo_cmd {
>>> +       uint8_t num_of_cmds;
>>> +       struct mmc_ioc_cmd *mmc_ioc_cmd_list;
>>> +};
>>
>> The size of this struct will depend on the pointer size of userspace.
>>
>> It might be better to use a u64 for the pointer instead. Otherwise
>> you'd need a compat ioctl wrapper to copy a 32-bit pointer over on a
>> 64-bit kernel.
>
> Oh, good point. I have made this change today. I have also tested
> this now with a hacked version of mmc-utils to send a couple status
> commands back-to-back. I have tested on -next with ARM32 and on
> ARM64 with an older 3.18 kernel (due to lack of mmc support in the
> mainline for my ARM64 board) and seems to be working fine. Here is
> an updated version ...
>
> Jon
>
> From fe5849a0d91ebbcfd092c74696f3fa7d7de3a156 Mon Sep 17 00:00:00 2001
> From: Seshagiri Holi <sholi@xxxxxxxxxx>
> Date: Mon, 4 Nov 2013 17:27:43 +0530
> Subject: [PATCH] mmc: block: Add new ioctl to send combo 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 combo commands are simple array of
> the existing mmc_ioc_cmd structure.
>
> Signed-off-by: Seshagiri Holi <sholi@xxxxxxxxxx>
> [ jonathanh@xxxxxxxxxx: Rebased on linux-next from v3.18. Changed
>   userspace pointer type for combo command to be a u64. Updated
>   commit message ]
> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> ---
>  drivers/mmc/card/block.c       | 199 ++++++++++++++++++++++++++++++++---------
>  include/uapi/linux/mmc/ioctl.h |  17 +++-
>  2 files changed, 171 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index c742cfd7674e..0423d95ea020 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -387,6 +387,22 @@ out:
>         return ERR_PTR(err);
>  }
>
> +static int mmc_blk_ioctl_copy_to_user(struct mmc_ioc_cmd __user *ic_ptr,
> +                                     struct mmc_blk_ioc_data *idata)
> +{
> +       if (copy_to_user(&(ic_ptr->response), idata->ic.response,
> +                        sizeof(idata->ic.response)))
> +               return -EFAULT;
> +
> +       if (!idata->ic.write_flag) {
> +               if (copy_to_user((void __user *)(unsigned long)idata->ic.data_ptr,
> +                                idata->buf, idata->buf_bytes))
> +                       return -EFAULT;
> +       }
> +
> +       return 0;
> +}
> +
>  static int ioctl_rpmb_card_status_poll(struct mmc_card *card, u32 *status,
>                                        u32 retries_max)
>  {
> @@ -447,12 +463,9 @@ out:
>         return err;
>  }
>
> -static int mmc_blk_ioctl_cmd(struct block_device *bdev,
> -       struct mmc_ioc_cmd __user *ic_ptr)
> +static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
> +                              struct mmc_blk_ioc_data *idata)
>  {
> -       struct mmc_blk_ioc_data *idata;
> -       struct mmc_blk_data *md;
> -       struct mmc_card *card;
>         struct mmc_command cmd = {0};
>         struct mmc_data data = {0};
>         struct mmc_request mrq = {NULL};
> @@ -461,33 +474,12 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         int is_rpmb = false;
>         u32 status = 0;
>
> -       /*
> -        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> -        * whole block device, not on a partition.  This prevents overspray
> -        * between sibling partitions.
> -        */
> -       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> -               return -EPERM;
> -
> -       idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
> -       if (IS_ERR(idata))
> -               return PTR_ERR(idata);
> -
> -       md = mmc_blk_get(bdev->bd_disk);
> -       if (!md) {
> -               err = -EINVAL;
> -               goto cmd_err;
> -       }
> +       if (!card || !md || !idata)
> +               return -EINVAL;
>
>         if (md->area_type & MMC_BLK_DATA_AREA_RPMB)
>                 is_rpmb = true;
>
> -       card = md->queue.card;
> -       if (IS_ERR(card)) {
> -               err = PTR_ERR(card);
> -               goto cmd_done;
> -       }
> -
>         cmd.opcode = idata->ic.opcode;
>         cmd.arg = idata->ic.arg;
>         cmd.flags = idata->ic.flags;
> @@ -582,18 +574,7 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         if (idata->ic.postsleep_min_us)
>                 usleep_range(idata->ic.postsleep_min_us, idata->ic.postsleep_max_us);
>
> -       if (copy_to_user(&(ic_ptr->response), cmd.resp, sizeof(cmd.resp))) {
> -               err = -EFAULT;
> -               goto cmd_rel_host;
> -       }
> -
> -       if (!idata->ic.write_flag) {
> -               if (copy_to_user((void __user *)(unsigned long) idata->ic.data_ptr,
> -                                               idata->buf, idata->buf_bytes)) {
> -                       err = -EFAULT;
> -                       goto cmd_rel_host;
> -               }
> -       }
> +       memcpy(&(idata->ic.response), cmd.resp, sizeof(cmd.resp));
>
>         if (is_rpmb) {
>                 /*
> @@ -609,6 +590,48 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>
>  cmd_rel_host:
>         mmc_put_card(card);
> +       return err;
> +}
> +
> +static int mmc_blk_ioctl_cmd(struct block_device *bdev,
> +                       struct mmc_ioc_cmd __user *ic_ptr)
> +{
> +       struct mmc_blk_ioc_data *idata;
> +       struct mmc_blk_data *md;
> +       struct mmc_card *card;
> +       int err;
> +
> +       /*
> +        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> +        * whole block device, not on a partition.  This prevents overspray
> +        * between sibling partitions.
> +        */
> +       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> +               return -EPERM;
> +
> +       idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
> +       if (IS_ERR(idata))
> +               return PTR_ERR(idata);
> +
> +       md = mmc_blk_get(bdev->bd_disk);
> +       if (!md) {
> +               err = -EINVAL;
> +               goto cmd_err;
> +       }
> +
> +       card = md->queue.card;
> +       if (IS_ERR(card)) {
> +               err = PTR_ERR(card);
> +               goto cmd_done;
> +       }
> +
> +       mmc_claim_host(card->host);

As __mmc_blk_ioctl_cmd() already does mmc_get_card(), you don't need
mmc_claim_host() here.

> +
> +       err = __mmc_blk_ioctl_cmd(card, md, idata);
> +
> +       mmc_release_host(card->host);

As __mmc_blk_ioctl_cmd() already does mmc_put_card(), you don't need
mmc_release_host() here.

> +
> +       err = mmc_blk_ioctl_copy_to_user(ic_ptr, idata);
>
>  cmd_done:
>         mmc_blk_put(md);
> @@ -618,13 +641,101 @@ cmd_err:
>         return err;
>  }
>
> +static int mmc_blk_ioctl_combo_cmd(struct block_device *bdev,
> +                                  struct mmc_ioc_combo_cmd __user *user)
> +{
> +       struct mmc_ioc_combo_cmd mcci = {0};
> +       struct mmc_blk_ioc_data **ioc_data = NULL;
> +       struct mmc_ioc_cmd __user *usr_ptr;
> +       struct mmc_card *card;
> +       struct mmc_blk_data *md;
> +       int i, err = -EFAULT;
> +       u8 n_cmds = 0;
> +
> +       /*
> +        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> +        * whole block device, not on a partition.  This prevents overspray
> +        * between sibling partitions.
> +        */
> +       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> +               return -EPERM;
> +
> +       if (copy_from_user(&mcci, user, sizeof(struct mmc_ioc_combo_cmd)))
> +               return -EFAULT;
> +
> +       if (!mcci.num_of_cmds) {
> +               err = -EINVAL;
> +               goto cmd_err;
> +       }
> +
> +       ioc_data = kcalloc(mcci.num_of_cmds, sizeof(*ioc_data), GFP_KERNEL);
> +       if (!ioc_data) {
> +               err = -ENOMEM;
> +               goto cmd_err;
> +       }
> +
> +       usr_ptr = (void * __user)(unsigned long)mcci.cmds_ptr;
> +       for (n_cmds = 0; n_cmds < mcci.num_of_cmds; n_cmds++) {
> +               ioc_data[n_cmds] =
> +                       mmc_blk_ioctl_copy_from_user(&usr_ptr[n_cmds]);
> +               if (IS_ERR(ioc_data[n_cmds])) {
> +                       err = PTR_ERR(ioc_data[n_cmds]);
> +                       goto cmd_err;
> +               }
> +       }
> +
> +       md = mmc_blk_get(bdev->bd_disk);
> +       if (!md)
> +               goto cmd_err;
> +
> +       card = md->queue.card;
> +       if (IS_ERR(card)) {
> +               err = PTR_ERR(card);
> +               goto cmd_done;
> +       }
> +
> +       mmc_claim_host(card->host);

Change to mmc_get_card().

> +       for (i = 0; i < n_cmds; i++) {
> +               err = __mmc_blk_ioctl_cmd(card, md, ioc_data[i]);
> +               if (err) {
> +                       mmc_release_host(card->host);
> +                       goto cmd_done;
> +               }
> +       }
> +
> +       mmc_release_host(card->host);

Change to mmc_put_card().

> +
> +       /* copy to user if data and response */
> +       for (i = 0; i < n_cmds; i++) {
> +               err = mmc_blk_ioctl_copy_to_user(&usr_ptr[i], ioc_data[i]);
> +               if (err)
> +                       break;
> +       }
> +
> +cmd_done:
> +       mmc_blk_put(md);
> +cmd_err:
> +       for (i = 0; i < n_cmds; i++) {
> +               kfree(ioc_data[i]->buf);
> +               kfree(ioc_data[i]);
> +       }
> +       kfree(ioc_data);
> +       return err;
> +}
> +
>  static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
>         unsigned int cmd, unsigned long arg)
>  {
> -       int ret = -EINVAL;
> -       if (cmd == MMC_IOC_CMD)
> -               ret = mmc_blk_ioctl_cmd(bdev, (struct mmc_ioc_cmd __user *)arg);
> -       return ret;
> +       switch (cmd) {
> +       case MMC_IOC_CMD:
> +               return mmc_blk_ioctl_cmd(bdev,
> +                               (struct mmc_ioc_cmd __user *)arg);
> +       case MMC_IOC_COMBO_CMD:
> +               return mmc_blk_ioctl_combo_cmd(bdev,
> +                               (struct mmc_ioc_combo_cmd __user *)arg);
> +       default:
> +               return -EINVAL;
> +       }
>  }
>
>  #ifdef CONFIG_COMPAT

Don't forget to build with this configuration as well, I don't think
you have. :-)

> diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h
> index 1f5e68923929..593e665177e2 100644
> --- a/include/uapi/linux/mmc/ioctl.h
> +++ b/include/uapi/linux/mmc/ioctl.h
> @@ -45,8 +45,23 @@ 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_combo_cmd - combo command information
> + * @cmds_ptr: Address of the location where the list of commands resides
> + * @num_of_cmds: number of commands to send
> + */
> +struct mmc_ioc_combo_cmd {
> +       __u64 cmds_ptr;
> +       uint8_t num_of_cmds;
> +};
>
> +#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
> +/*
> + * MMC_COMBO_IOC_CMD: Used to send an array of MMC commands described by
> + *     the structure mmc_ioc_combo_cmd. The MMC driver will issue all
> + *     commands in array in sequence to card.
> + */
> +#define MMC_IOC_COMBO_CMD _IOWR(MMC_BLOCK_MAJOR, 1, struct mmc_ioc_combo_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
> --
> 2.1.4
>

Kind regards
Uffe
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