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SubjectRe: [PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info
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Hi John,

John Stultz <john.stultz@linaro.org> writes:

> From: San Mehat <san@google.com>
>
> This patch has been carried in the Android tree for quite some
> time and is one of the few patches required to get a mainline
> kernel up and running with an exsiting Android userspace. So I
> wanted to submit it for review and consideration if it should
> be merged.
>
> For disk devices, a new uevent parameter 'NPARTS' specifies the number
> of partitions detected by the kernel. Partition devices get 'PARTN' which
> specifies the partitions index in the table, and 'PARTNAME', which
> specifies PARTNAME specifices the partition name of a partition device
>
> Android's userspace uses this for creating device node links from the
> partition name and number: ie:
> /dev/block/platform/soc/by-name/system
> or
> /dev/block/platform/soc/by-num/p1
>
> One can see its usage here:
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#355
> and
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#494

Those links don't appear to use the NPARTS uevent parameter, unless I
missed it.

> Thoughts and feedback would be greatly appreciated!

I can't say I have strong feelings one way or the other. I've CC'd Kay
and Harald, hoping they might have an opinion.

Cheers,
Jeff

>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Rom Lemarchand <romlem@google.com>
> Cc: Android Kernel Team <kernel-team@android.com>
> Signed-off-by: Dima Zavin <dima@android.com>
> [jstultz: Added more context to commit message & whitespace fix]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> block/genhd.c | 17 +++++++++++++++++
> block/partition-generic.c | 11 +++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 0c706f3..248139e 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1115,6 +1115,22 @@ static void disk_release(struct device *dev)
> blk_put_queue(disk->queue);
> kfree(disk);
> }
> +
> +static int disk_uevent(struct device *dev, struct kobj_uevent_env *env)
> +{
> + struct gendisk *disk = dev_to_disk(dev);
> + struct disk_part_iter piter;
> + struct hd_struct *part;
> + int cnt = 0;
> +
> + disk_part_iter_init(&piter, disk, 0);
> + while ((part = disk_part_iter_next(&piter)))
> + cnt++;
> + disk_part_iter_exit(&piter);
> + add_uevent_var(env, "NPARTS=%u", cnt);
> + return 0;
> +}
> +
> struct class block_class = {
> .name = "block",
> };
> @@ -1134,6 +1150,7 @@ static struct device_type disk_type = {
> .groups = disk_attr_groups,
> .release = disk_release,
> .devnode = block_devnode,
> + .uevent = disk_uevent,
> };
>
> #ifdef CONFIG_PROC_FS
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index e771113..e5d91c9 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -216,10 +216,21 @@ static void part_release(struct device *dev)
> kfree(p);
> }
>
> +static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
> +{
> + struct hd_struct *part = dev_to_part(dev);
> +
> + add_uevent_var(env, "PARTN=%u", part->partno);
> + if (part->info && part->info->volname[0])
> + add_uevent_var(env, "PARTNAME=%s", part->info->volname);
> + return 0;
> +}
> +
> struct device_type part_type = {
> .name = "partition",
> .groups = part_attr_groups,
> .release = part_release,
> + .uevent = part_uevent,
> };
>
> static void delete_partition_rcu_cb(struct rcu_head *head)


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