From: Peter Ujfalusi <peter.ujfalusi@ti.com>
To: Vinod Koul <vkoul@kernel.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
dmaengine <dmaengine@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 0/3] dmaengine: Stear users towards dma_request_slave_chan()
Date: Wed, 5 Feb 2020 13:56:00 +0200 [thread overview]
Message-ID: <7b8d9ab2-1734-d54b-ab6e-b620866ce0ce@ti.com> (raw)
In-Reply-To: <20200205113155.GE2618@vkoul-mobl>
Hi Vinod,
On 05/02/2020 13.31, Vinod Koul wrote:
>> Looking at the commit which added it and I still don't get the point.
>> If any of the channel is in use then we should not allow the DMA driver
>> to go away at all.
>
> Not really, if the device is already gone, we cant do much about it. We
> have to handle that gracefully rather than oopsing
Ah, I have not thought about that. True.
> The important part is that the device is gone. Think about a device on
> PCI card which is yanked off or a USB device unplugged. Device is
> already gone, you can't communicate with it anymore. So all we can do is
> handle the condition and exit, hence the new method to let driver know.
But for most devices this is not applicable, I also wondered what should
I do in order to silence the print. Just add an empty device_release?
>> Imho there should be a function to check if we can proceed with the
>> .remove of the driver and fail it if any of the channels are in use.
>>
>> Hrm, base/dd.c __device_release_driver() does not check the .remove's
>> return value, so it can not fail.
>>
>> What is expected if the .remove returns with OK but we still have
>> channels in use?
>>
>> After the remove all sorts of things got yanked which might makes the
>> still in use channels cause issues down the road.
>>
>> I'm curious why it is a good thing to remotely try to support unbind
>> when the driver is in use.
>> It is like one wants to support ext4 removal even when your rootfs is ext4.
>>
>> I think krefing the DMA driver for channel request/release is just fine,
>> if user wants to break the system we should not assist...
>>
>>>> It's not limited to that driver, but actually all I'm maintaining.
>>>>
>>>> Users are not happy!
>>>>
>>>> --
>>>> With Best Regards,
>>>> Andy Shevchenko
>>>
>>
>> - Péter
>>
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>
- Péter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
next prev parent reply other threads:[~2020-02-05 11:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-03 10:18 [PATCH 0/3] dmaengine: Stear users towards dma_request_slave_chan() Peter Ujfalusi
2020-02-03 10:18 ` [PATCH 1/3] dmaengine: Remove unused define for dma_request_slave_channel_reason() Peter Ujfalusi
2020-02-03 13:35 ` Geert Uytterhoeven
2020-02-03 10:18 ` [PATCH 2/3] dmaengine: Mark dma_request_slave_channel() deprecated Peter Ujfalusi
2020-02-03 10:18 ` [PATCH 3/3] dmaengine: Encourage dma_request_slave_channel_compat() users to migrate Peter Ujfalusi
2020-02-03 10:35 ` Andy Shevchenko
2020-02-03 10:37 ` [PATCH 0/3] dmaengine: Stear users towards dma_request_slave_chan() Andy Shevchenko
2020-02-03 10:59 ` Peter Ujfalusi
2020-02-03 11:16 ` Andy Shevchenko
2020-02-03 12:09 ` Peter Ujfalusi
2020-02-03 12:48 ` Andy Shevchenko
2020-02-03 13:32 ` Geert Uytterhoeven
2020-02-03 20:21 ` John Paul Adrian Glaubitz
2020-02-03 20:34 ` Geert Uytterhoeven
2020-02-03 21:26 ` John Paul Adrian Glaubitz
2020-02-04 8:13 ` Geert Uytterhoeven
2020-02-04 6:52 ` Peter Ujfalusi
2020-02-04 8:01 ` Geert Uytterhoeven
2020-02-04 8:15 ` Peter Ujfalusi
2020-02-04 8:21 ` Peter Ujfalusi
2020-02-04 9:16 ` Rob Landley
2020-02-04 9:27 ` Geert Uytterhoeven
2020-02-04 10:18 ` Rob Landley
2020-02-04 6:21 ` Vinod Koul
2020-02-04 11:21 ` Andy Shevchenko
2020-02-05 4:43 ` Vinod Koul
2020-02-05 8:10 ` Peter Ujfalusi
2020-02-05 11:31 ` Vinod Koul
2020-02-05 11:56 ` Peter Ujfalusi [this message]
2020-02-05 11:59 ` Vinod Koul
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7b8d9ab2-1734-d54b-ab6e-b620866ce0ce@ti.com \
--to=peter.ujfalusi@ti.com \
--cc=andy.shevchenko@gmail.com \
--cc=dan.j.williams@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=vkoul@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).