Re: [PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[John Stultz]

On Mon, Nov 2, 2015 at 10:03 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
> Hi John,
>
> John Stultz <john.stultz@xxxxxxxxxx> writes:
>
>> From: San Mehat <san@xxxxxxxxxx>
>>
>> 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.

So good point! It looks like with Android Marshmallow they dropped using NPARTS.
For context, here is where it was used with Lollipop:
   http://androidxref.com/5.1.1_r6/xref/system/vold/DirectVolume.cpp#192

Unless Rom or someone on the Android team objects, I'll remove that
chunk from the patch and re-submit.

Thanks for the review!
-john
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