linux-kernel - Re: [PATCH 11/14] staging: android: ion: Allow heap name to be null

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Message-ID: <042dd3b1-9a41-2a76-270d-1c992d782c40@redhat.com>
Date:   Fri, 18 Jan 2019 11:53:33 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     "Andrew F. Davis" <afd@...com>,
        Brian Starkey <Brian.Starkey@....com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        nd <nd@....com>
Subject: Re: [PATCH 11/14] staging: android: ion: Allow heap name to be null

On 1/16/19 9:12 AM, Andrew F. Davis wrote:
> On 1/16/19 9:28 AM, Brian Starkey wrote:
>> Hi Andrew,
>>
>> On Fri, Jan 11, 2019 at 12:05:20PM -0600, Andrew F. Davis wrote:
>>> The heap name can be used for debugging but otherwise does not seem
>>> to be required and no other part of the code will fail if left NULL
>>> except here. We can make it required and check for it at some point,
>>> for now lets just prevent this from causing a NULL pointer exception.
>>
>> I'm not so keen on this one. In the "new" API with heap querying, the
>> name string is the only way to identify the heap. I think Laura
>> mentioned at XDC2017 that it was expected that userspace should use
>> the strings to find the heap they want.
>>
> 
> Right now the names are only for debug. I accidentally left the name
> null once and got a kernel crash. This is the only spot where it is
> needed so I fixed it up. The other option is to make the name mandatory
> and properly error out, I don't want to do that right now until the
> below discussion is had to see if names really do matter or not.
> 

Yes, the heap names are part of the query API and are the expected
way to identify individual heaps for the API at the moment so having
a null heap name is incorrect. The heap name seemed like the best way
to identify heaps to userspace but if you have an alternative proposal
I'd be interested.

Thanks,
Laura

>