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Date:   Tue, 3 Mar 2020 09:57:25 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc:     dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
        dan.j.williams@intel.com, geert@linux-m68k.org
Subject: Re: [PATCH v4 1/2] dmaengine: Add basic debugfs support
Message-ID: <20200303042725.GM4148@vkoul-mobl>
References: <20200228130747.22905-1-peter.ujfalusi@ti.com>
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 <20200302071146.GE4148@vkoul-mobl>
 <7b4f244d-0855-f979-414d-e2d3cb0f0c2f@ti.com>
 <be7d4df5-121b-0eec-b68c-fa3b5cffc8c9@ti.com>
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On 02-03-20, 13:53, Peter Ujfalusi wrote:
> 
> 
> On 02/03/2020 12.28, Peter Ujfalusi wrote:
> > Hi Vinod,
> > 
> > On 02/03/2020 9.11, Vinod Koul wrote:
> >>> diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
> >>> index e8a320c9e57c..72cd7fe33638 100644
> >>> --- a/drivers/dma/dmaengine.h
> >>> +++ b/drivers/dma/dmaengine.h
> >>> @@ -182,4 +182,10 @@ dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
> >>>  struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
> >>>  struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
> >>>  
> >>> +#ifdef CONFIG_DEBUG_FS
> >>> +#include <linux/debugfs.h>
> >>> +
> >>> +struct dentry *dmaengine_get_debugfs_root(void);
> >>
> >> this needs to have an else defined with NULL return so that we dont
> >> force users to wrap the code under CONFIG_DEBUG_FS..
> > 
> > Drivers would anyways should have their debugfs related code wrapped
> > within ifdef. There is no point of having the code complied when it can
> > not be used (no debugfs support).
> > 
> > But I can add the  else case if we really want to:
> > 
> > #ifdef CONFIG_DEBUG_FS
> > #include <linux/debugfs.h>
> > 
> > struct dentry *dmaengine_get_debugfs_root(void);
> > 
> > #else
> > struct dentry;
> > static inline struct dentry *dmaengine_get_debugfs_root(void)
> > {
> > 	return NULL;
> > }
> > #endif /* CONFIG_DEBUG_FS */
> 
> It might be even better if the core creates directories for the dma
> controllers in dma_async_device_register() and removes the whole
> directory in dma_async_device_unregister()

hmmm, i think makes sense and dentry can be part of dma_device

> 
> Then drivers can get their per device root via:
> #ifdef CONFIG_DEBUG_FS
> static inline struct dentry *
> dmaengine_get_debugfs_root(struct dma_device *dma_dev) {
> 	return dma_dev->dbg_dev_root;
> }

right!

> #else
> struct dentry;
> static inline struct dentry *
> dmaengine_get_debugfs_root(struct dma_device *dma_dev)
> {
> 	return NULL;
> }
> #endif /* CONFIG_DEBUG_FS */

-- 
~Vinod