linux-kernel - Re: [alsa-devel] [PATCH] soundwire: bus: fix device number leak on errors

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Message-ID: <0f53a197-bd2d-a181-b39c-5ebe99458eac@linux.intel.com>
Date:   Tue, 14 Jan 2020 10:10:40 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     alsa-devel@...a-project.org, tiwai@...e.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        broonie@...nel.org, srinivas.kandagatla@...aro.org,
        jank@...ence.com, slawomir.blauciak@...el.com,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>
Subject: Re: [alsa-devel] [PATCH] soundwire: bus: fix device number leak on
 errors



On 1/14/20 12:37 AM, Vinod Koul wrote:
> On 13-01-20, 16:56, Pierre-Louis Bossart wrote:
>> If the programming of the dev_number fails due to an IO error, a new
>> device_number will be assigned, resulting in a leak.
>>
>> Make sure we only assign a device_number once per Slave device.
> 
> Although I am not sure if this would be a leak, we assign a new num and
> old number should have gotten recycled as they would be unattached
> status.

When you program the device number and it fails, there is still a 
Device0 reporting as attached, so you will loop and try to assign a new 
device number. In this case there is never a transition to UNATTACHED, 
the Slave remains ATTACHED as Device0 until the enumeration succeed with 
a successful non-zero device number.

This only happened to us w/ early prototypes where the PCB routing was 
questionable and the speed too high, but still it's useful to keep this 
device number constant

> Anyway this is good improvement as it helps to debug having same
> dev_num, so Applied, thanks

Thanks.