linux-kernel - Re: [PATCH] dmaengine: remove debugfs #ifdef

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Date:   Mon, 20 Sep 2021 15:47:07 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Hyun Kwon <hyun.kwon@...inx.com>, Vinod Koul <vkoul@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Sanjay R Mehta <sanju.mehta@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Arnd Bergmann <arnd@...db.de>,
        Jianqiang Chen <jianqiang.chen@...inx.com>,
        Quanyang Wang <quanyang.wang@...driver.com>,
        Yang Li <yang.lee@...ux.alibaba.com>,
        Allen Pais <apais@...ux.microsoft.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Biju Das <biju.das.jz@...renesas.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: remove debugfs #ifdef

Hi Arnd,

Thank you for the patch.

On Mon, Sep 20, 2021 at 02:20:07PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The ptdma driver has added debugfs support, but this fails to build
> when debugfs is disabled:
> 
> drivers/dma/ptdma/ptdma-debugfs.c: In function 'ptdma_debugfs_setup':
> drivers/dma/ptdma/ptdma-debugfs.c:93:54: error: 'struct dma_device' has no member named 'dbg_dev_root'
>    93 |         debugfs_create_file("info", 0400, pt->dma_dev.dbg_dev_root, pt,
>       |                                                      ^
> drivers/dma/ptdma/ptdma-debugfs.c:96:55: error: 'struct dma_device' has no member named 'dbg_dev_root'
>    96 |         debugfs_create_file("stats", 0400, pt->dma_dev.dbg_dev_root, pt,
>       |                                                       ^
> drivers/dma/ptdma/ptdma-debugfs.c:102:52: error: 'struct dma_device' has no member named 'dbg_dev_root'
>   102 |                 debugfs_create_dir("q", pt->dma_dev.dbg_dev_root);
>       |                                                    ^
>
> Remove the #ifdef in the header, as this only saves a few bytes,
> but would require ugly #ifdefs in each driver using it.
> Simplify the other user while we're at it.
> 
> Fixes: e2fb2e2a33fa ("dmaengine: ptdma: Add debugfs entries for PTDMA")
> Fixes: 26cf132de6f7 ("dmaengine: Create debug directories for DMA devices")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/dma/xilinx/xilinx_dpdma.c | 15 +--------------
>  include/linux/dmaengine.h         |  2 --
>  2 files changed, 1 insertion(+), 16 deletions(-)
> 
> diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
> index b280a53e8570..ce5c66e6897d 100644
> --- a/drivers/dma/xilinx/xilinx_dpdma.c
> +++ b/drivers/dma/xilinx/xilinx_dpdma.c
> @@ -271,9 +271,6 @@ struct xilinx_dpdma_device {
>  /* -----------------------------------------------------------------------------
>   * DebugFS
>   */
> -
> -#ifdef CONFIG_DEBUG_FS
> -

It's only a few bytes of data in struct dma_device, but a bit more in
.text here. Is the simplification really required in this driver ?

>  #define XILINX_DPDMA_DEBUGFS_READ_MAX_SIZE	32
>  #define XILINX_DPDMA_DEBUGFS_UINT16_MAX_STR	"65535"
>  
> @@ -299,7 +296,7 @@ struct xilinx_dpdma_debugfs_request {
>  
>  static void xilinx_dpdma_debugfs_desc_done_irq(struct xilinx_dpdma_chan *chan)
>  {
> -	if (chan->id == dpdma_debugfs.chan_id)
> +	if (IS_ENABLED(CONFIG_DEBUG_FS) && chan->id == dpdma_debugfs.chan_id)
>  		dpdma_debugfs.xilinx_dpdma_irq_done_count++;
>  }
>  
> @@ -462,16 +459,6 @@ static void xilinx_dpdma_debugfs_init(struct xilinx_dpdma_device *xdev)
>  		dev_err(xdev->dev, "Failed to create debugfs testcase file\n");
>  }
>  
> -#else
> -static void xilinx_dpdma_debugfs_init(struct xilinx_dpdma_device *xdev)
> -{
> -}
> -
> -static void xilinx_dpdma_debugfs_desc_done_irq(struct xilinx_dpdma_chan *chan)
> -{
> -}
> -#endif /* CONFIG_DEBUG_FS */
> -
>  /* -----------------------------------------------------------------------------
>   * I/O Accessors
>   */
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index e5c2c9e71bf1..9000f3ffce8b 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -944,10 +944,8 @@ struct dma_device {
>  	void (*device_issue_pending)(struct dma_chan *chan);
>  	void (*device_release)(struct dma_device *dev);
>  	/* debugfs support */
> -#ifdef CONFIG_DEBUG_FS
>  	void (*dbg_summary_show)(struct seq_file *s, struct dma_device *dev);
>  	struct dentry *dbg_dev_root;
> -#endif
>  };
>  
>  static inline int dmaengine_slave_config(struct dma_chan *chan,

-- 
Regards,

Laurent Pinchart