From: Dan Williams <djbw@fb.com>
To: Jon Mason <jon.mason@intel.com>
Cc: Vinod Koul <vinod.koul@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] dmadevices: dma_sync_wait undefined
Date: Tue, 18 Jun 2013 18:13:28 -0700 [thread overview]
Message-ID: <CAA9_cmc1Gu=BnM_OpMuqL7Hcjz-kfqxJtZzGHP8Nh-hc+tCWeA@mail.gmail.com> (raw)
In-Reply-To: <1371602813-19828-2-git-send-email-jon.mason@intel.com>
On Tue, Jun 18, 2013 at 5:46 PM, Jon Mason <jon.mason@intel.com> wrote:
> dma_sync_wait is declared regardless of whether CONFIG_DMA_ENGINE is
> enabled, but calling the function without CONFIG_DMA_ENGINE enabled
> results in the following gcc error.
> ERROR: "dma_sync_wait" [drivers/ntb/ntb.ko] undefined!
>
> To get around this, declare dma_sync_wait as an inline function if
> CONFIG_DMA_ENGINE is undefined.
>
> Signed-off-by: Jon Mason <jon.mason@intel.com>
> Acked-by: Dave Jiang <dave.jiang@intel.com>
> ---
> include/linux/dmaengine.h | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 96d3e4a..e3652ac 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -963,8 +963,8 @@ dma_set_tx_state(struct dma_tx_state *st, dma_cookie_t last, dma_cookie_t used,
> }
> }
>
> -enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
> #ifdef CONFIG_DMA_ENGINE
> +enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
> enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
> void dma_issue_pending_all(void);
> struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
> @@ -972,6 +972,10 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
> struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
> void dma_release_channel(struct dma_chan *chan);
> #else
> +static inline enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie)
> +{
> + return DMA_SUCCESS;
> +}
Seems like something we should fix, but why is this not an indication
that the code calling this is missing a "depends on DMA_ENGINE".
On second look dma_sync_wait is a use as last resort hack that
probably should not escape its internal use in dmaengine.c. The other
escape in drivers/media/platform/timblogiw.c already looks problematic
by having a live cpu spin immediately following a sleeping wait,
obviously something event based was wanted. What's the use case in
NTB?
--
Dan
next prev parent reply other threads:[~2013-06-19 1:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-19 0:46 [PATCH 0/2] DMA Offload fixes Jon Mason
2013-06-19 0:46 ` [PATCH 1/2] dmadevices: dma_sync_wait undefined Jon Mason
2013-06-19 1:13 ` Dan Williams [this message]
2013-06-19 16:28 ` Jon Mason
2013-06-20 21:20 ` Dan Williams
2013-06-26 23:47 ` Jon Mason
2013-06-19 0:46 ` [PATCH 2/2] ioatdma: add DMA_PRIVATE capabilities flag Jon Mason
2013-06-19 0:59 ` Dan Williams
2013-06-19 17:36 ` Dave Jiang
2013-06-19 17:52 ` Jon Mason
2013-06-19 18:56 ` Dan Williams
2013-06-19 20:10 ` Jon Mason
2013-06-19 20:44 ` Dan Williams
2013-06-26 23:55 ` Jon Mason
2013-06-27 1:10 ` Dan Williams
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