-----Original Message----- From: Andy Shevchenko andriy.shevchenko@linux.intel.com Sent: Tuesday, July 21, 2020 10:47 AM To: Ruhl, Michael J michael.j.ruhl@intel.com Cc: dri-devel@lists.freedesktop.org; Andrew Morton <akpm@linux- foundation.org>; Mike Rapoport rppt@linux.ibm.com; Chris Wilson chris@chris-wilson.co.uk; stable@vger.kernel.org Subject: Re: [PATCH] io-mapping: Indicate mapping failure
On Tue, Jul 21, 2020 at 10:16:41AM -0400, Michael J. Ruhl wrote:
Sometimes it is good to know when your mapping failed.
Can you elaborate...
Sure, guess I was too glib. 😊
Currently the io_mapping_init_wc (the !ATOMIC_IOMAP version), function will always return success.
If the setting of the iomem (from ioremap_wc) fails, the only way for the caller to know is to check the value of iomap->iomem.
Since all of the callers expect a NULL return on error, and check for a NULL, I felt this needed a fixes (i.e. unexpected behavior).
Fixes: cafaf14a5d8f ("io-mapping: Always create a struct to hold metadata
about the io-mapping"
...especially taking into account that Fixes implies regression / bug?
The failure (in my case a crash) is not revealed until the address is accessed long after the init.
I will update the commit.
Mike
-- With Best Regards, Andy Shevchenko