From: Jeffrey Hugo <jhugo@codeaurora.org>
To: Loic Poulain <loic.poulain@linaro.org>,
manivannan.sadhasivam@linaro.org, hemantk@codeaurora.org
Cc: linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] bus: mhi: core: Indexed MHI controller name
Date: Wed, 25 Nov 2020 08:49:36 -0700 [thread overview]
Message-ID: <005093de-c8e4-2075-050a-5998a3cbcfcc@codeaurora.org> (raw)
In-Reply-To: <1093835e-3ed6-5579-5fbe-39a6d8fbadaf@codeaurora.org>
On 11/25/2020 8:42 AM, Jeffrey Hugo wrote:
> On 11/25/2020 8:43 AM, Loic Poulain wrote:
>> Today the MHI controller name is simply cloned from the underlying
>> bus device (its parent), that gives the following device structure
>> for e.g. a MHI/PCI controller:
>> devices/pci0000:00/0000:00:01.2/0000:02:00.0/0000:02:00.0
>> devices/pci0000:00/0000:00:01.2/0000:02:00.0/0000:02:00.0/0000:02:00.0_IPCR
>>
>> ...
>>
>> That's quite misleading/confusing and can cause device registering
>> issues because of duplicate dev name (e.g. if a PCI device register
>> two different MHI instances).
>>
>> This patch changes MHI core to create indexed mhi controller names
>> (mhi0, mhi1...) in the same way as other busses (i2c0, usb0...).
>>
>> The previous example becomes:
>> devices/pci0000:00/0000:00:01.2/0000:02:00.0/mhi0
>> devices/pci0000:00/0000:00:01.2/0000:02:00.0/mhi0/mhi0_IPCR
>> ...
>>
>> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
>
>
> How does this change /sys/bus/mhi/devices/ ?
>
> The point of having the bus name in the mhi device name is to give an
> easy way to correlate those devices back to the "root" device (I have a
> lot of users which do that).
>
> Also, do we actually have some device that actually exposes multiple MHI
> interfaces?
>
>
Looking at the code change itself, looks like the controller index is
essentially random, and not persistent. Is that expected?
I'm thinking it might be confusing if you have say 12 MHI controllers
from 12 different devices, and some of those devices crash at roughly
the same time. The controllers get removed, and re-initialized, which
means that you have essentially a race condition where the controller
for the same device now has a different index.
--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2020-11-25 15:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 15:43 [PATCH] bus: mhi: core: Indexed MHI controller name Loic Poulain
2020-11-25 15:42 ` Jeffrey Hugo
2020-11-25 15:49 ` Jeffrey Hugo [this message]
2020-11-25 16:23 ` Loic Poulain
2020-11-25 16:26 ` Jeffrey Hugo
2020-11-25 16:15 ` Loic Poulain
2020-11-25 16:24 ` Jeffrey Hugo
2020-11-25 17:14 ` Jeffrey Hugo
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