linux-kernel - Regression: ABI: /sys/module/mmcblk changed to /sys/module/mmc

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Message-ID: <CALAqxLWyk0iQsYbsyvOT0TK2bChLH7KqwQMHwf+SDX8jds7qyQ@mail.gmail.com>
Date:	Wed, 10 Feb 2016 23:29:24 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Ulf Hansson <ulf.hansson@...aro.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Regression: ABI: /sys/module/mmcblk changed to /sys/module/mmc_block

I recently noticed with 4.4 based kernel's Android's userspace wasn't
able to properly detect micro-SD cards when they were inserted.

This is due to vold not being able to access
/sys/module/mmcblk/parameters/perdev_minors

See: http://androidxref.com/6.0.1_r10/xref/system/vold/Disk.cpp#49

Looking into it, it seems commit 829b6962f7e3cfc ("mmc: block: don't
use parameter prefix if built as module") changed the behavior,
resulting in the userspace path changing to:
"/sys/module/mmc_block/..."

This seems like an ABI regression, which is breaking existing userspace.

So... Probably something to revert?

thanks
-john