From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] DMA: add help function to check whether dma controller registered
Date: Fri, 02 Aug 2013 13:59:59 -0600 [thread overview]
Message-ID: <51FC0FBF.9010107@wwwdotorg.org> (raw)
In-Reply-To: <1375423458-6868-1-git-send-email-rizhao@nvidia.com>
On 08/02/2013 12:04 AM, Richard Zhao wrote:
> DMA client device driver usually needs to know at probe time whether
> dma controller has been registered to deffer probe. So add a help
> function of_dma_check_controller.
>
> DMA request channel functions can also used to check it, but they
> are usually called at open() time.
> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> index e1c4d3b..b6828c1 100644
> +int of_dma_check_controller(struct device *dev, const char *name)
> + for (i = 0; i < count; i++) {
> + if (of_dma_match_channel(np, name, i, &dma_spec))
> + continue;
> +
> + mutex_lock(&of_dma_lock);
> + ofdma = of_dma_find_controller(&dma_spec);
> + mutex_unlock(&of_dma_lock);
> + of_node_put(dma_spec.np);
Do we need to add the following here:
if (ofdma)
break
To ensure that as soon as a successful match is found, the loop exits?
Otherwise, if there are multiple providers for that name, and the first
N are registered but the last isn't, this function will still return
failure.
> + if (ofdma)
> + return 0;
> + else
> + return -ENODEV;
That probably should be -EPROBE_DEFER?
Although, what about differentiating between "entry not found by
of_dma_match_channel" and "controller not yet probed"?
next prev parent reply other threads:[~2013-08-02 19:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-02 6:04 [PATCH] DMA: add help function to check whether dma controller registered Richard Zhao
2013-08-02 19:59 ` Stephen Warren [this message]
2013-08-05 5:56 ` Richard Zhao
2013-08-22 6:43 ` [PATCH v2] " Richard Zhao
2013-08-22 20:36 ` Stephen Warren
2013-08-23 1:17 ` Richard Zhao
2013-08-23 15:56 ` Stephen Warren
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=51FC0FBF.9010107@wwwdotorg.org \
--to=swarren@wwwdotorg$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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