From: Vinod Koul <vinod.koul@intel.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
peter@hurleysoftware.com, Dan Williams <dan.j.williams@intel.com>,
dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
nsekhar@ti.com, linux-omap@vger.kernel.org,
linux-serial@vger.kernel.org, john.ogness@linutronix.de,
Peter Ujfalusi <peter.ujfalusi@ti.com>
Subject: Re: [PATCH 2/3] dma: add __must_check annotation for dmaengine_pause()
Date: Fri, 21 Aug 2015 14:02:45 +0530 [thread overview]
Message-ID: <20150821083245.GM13546@localhost> (raw)
In-Reply-To: <55C9EBD5.3090203@linutronix.de>
On Tue, Aug 11, 2015 at 02:34:29PM +0200, Sebastian Andrzej Siewior wrote:
> On 08/11/2015 12:06 PM, Russell King - ARM Linux wrote:
> > I think what people need to learn is that an API in the kernel which
> > returns an int _can_ fail - it returns an int so it _can_ return an
> > error code. If it _can_ return an error code, there _will_ be
> > implementations which _do_.
> >
> > If you don't check the return code, either your code doesn't care whether
> > the function was successful or not, or you're playing with fire. This is
> > a prime example of playing with fire.
> >
> > Let's leave the crappy userspace laziness with regard to error checking
> > to userspace, and keep it out of the kernel.
> >
> > Yes, the DMA engine capabilities may not be sufficient to describe every
> > detail of DMA engines, but that's absolutely no reason to skimp on error
> > checking. Had there been some kind of error checking at the site, this
> > problem would have been spotted before the 8250-omap driver was merged.
>
> Let me disable RX-DMA in 8250-omap code and push that stable. Then we
> won't need a special annotation for pause support because it remains
> off and is currently about one user. I browsed each driver in
> drivers/dma each one which does support pause supports it and all of
> them implement it unconditionally (ipu_idmac grabs a mutex first but
> this is another story).
> Adding error checking to 8250-omap like I have it in #1 and disabling
> RX-DMA in case pause fails looks be reasonable since there is nothing
> else that can be done I guess.
> Once we have the missing piece in omap-dma the RX-DMA can be enabled in
> 8250-omap.
> Does this sound like a plan we can agree on?
Yes sounds good to me..
--
~Vinod
next prev parent reply other threads:[~2015-08-21 8:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 20:00 omap-dma + 8250_omap: fix the dmaengine_pause() Sebastian Andrzej Siewior
2015-08-07 20:00 ` [PATCH 1/3] tty: serial: 8250_omap: do not use RX DMA if pause is not supported Sebastian Andrzej Siewior
2015-08-08 0:28 ` Peter Hurley
2015-08-08 9:03 ` Russell King - ARM Linux
2015-08-11 9:57 ` Vinod Koul
2015-08-08 9:32 ` Sebastian Andrzej Siewior
2015-08-08 9:57 ` Russell King - ARM Linux
2015-08-08 15:40 ` Greg KH
2015-08-10 11:54 ` Peter Ujfalusi
2015-08-10 12:19 ` Sebastian Andrzej Siewior
2015-08-10 13:00 ` Peter Hurley
2015-08-10 17:15 ` Russell King - ARM Linux
2015-08-07 20:00 ` [PATCH 2/3] dma: add __must_check annotation for dmaengine_pause() Sebastian Andrzej Siewior
2015-08-08 0:40 ` Peter Hurley
2015-08-11 9:58 ` Vinod Koul
2015-08-11 10:06 ` Russell King - ARM Linux
2015-08-11 12:34 ` Sebastian Andrzej Siewior
2015-08-21 8:32 ` Vinod Koul [this message]
2015-08-07 20:00 ` [PATCH v3 3/3] dma: omap-dma: add support for pause of non-cyclic transfers Sebastian Andrzej Siewior
2015-08-11 12:02 ` Peter Ujfalusi
2015-08-11 12:30 ` Russell King - ARM Linux
2015-08-11 12:43 ` Peter Ujfalusi
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=20150821083245.GM13546@localhost \
--to=vinod.koul@intel.com \
--cc=bigeasy@linutronix.de \
--cc=dan.j.williams@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=john.ogness@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-omap@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=linux@arm.linux.org.uk \
--cc=nsekhar@ti.com \
--cc=peter.ujfalusi@ti.com \
--cc=peter@hurleysoftware.com \
/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).