linux-kernel - Re: [PATCH 13/25] dmaengine: dw-edma: Stop checking debugfs_create

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Message-ID: <20220324181255.GV2854@thinkpad>
Date:   Thu, 24 Mar 2022 23:42:55 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Li <Frank.Li@....com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/25] dmaengine: dw-edma: Stop checking
 debugfs_create_*() return value

On Thu, Mar 24, 2022 at 04:48:24AM +0300, Serge Semin wrote:
> First of all they never return NULL. So checking their return value for
> being not NULL just pointless. Secondly the DebugFS subsystem is designed
> in a way to be used as simple as possible. So if one of the
> debugfs_create_*() method in a hierarchy fails, the following methods will
> just silently return the passed erroneous parental dentry. Finally the
> code is supposed to be working no matter whether anything DebugFS-related
> fails. So in order to make code simpler and DebugFS-independent let's drop
> the debugfs_create_*() methods return value checking in the same way as
> the most of the kernel drivers do.
> 
> Note in order to preserve some memory space we suggest to skip the DebugFS
> nodes initialization if the file system in unavailable.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Man

> ---
>  drivers/dma/dw-edma/dw-edma-v0-debugfs.c | 20 +++++---------------
>  1 file changed, 5 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> index 12845a2dc016..808eed212be8 100644
> --- a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> +++ b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> @@ -100,9 +100,8 @@ static void dw_edma_debugfs_create_x32(const struct debugfs_entries entries[],
>  	int i;
>  
>  	for (i = 0; i < nr_entries; i++) {
> -		if (!debugfs_create_file_unsafe(entries[i].name, 0444, dir,
> -						entries[i].reg,	&fops_x32))
> -			break;
> +		debugfs_create_file_unsafe(entries[i].name, 0444, dir,
> +					   entries[i].reg, &fops_x32);
>  	}
>  }
>  
> @@ -168,8 +167,6 @@ static void dw_edma_debugfs_regs_wr(struct dentry *dir)
>  	char name[16];
>  
>  	regs_dir = debugfs_create_dir(WRITE_STR, dir);
> -	if (!regs_dir)
> -		return;
>  
>  	nr_entries = ARRAY_SIZE(debugfs_regs);
>  	dw_edma_debugfs_create_x32(debugfs_regs, nr_entries, regs_dir);
> @@ -184,8 +181,6 @@ static void dw_edma_debugfs_regs_wr(struct dentry *dir)
>  		snprintf(name, sizeof(name), "%s:%d", CHANNEL_STR, i);
>  
>  		ch_dir = debugfs_create_dir(name, regs_dir);
> -		if (!ch_dir)
> -			return;
>  
>  		dw_edma_debugfs_regs_ch(&regs->type.unroll.ch[i].wr, ch_dir);
>  
> @@ -237,8 +232,6 @@ static void dw_edma_debugfs_regs_rd(struct dentry *dir)
>  	char name[16];
>  
>  	regs_dir = debugfs_create_dir(READ_STR, dir);
> -	if (!regs_dir)
> -		return;
>  
>  	nr_entries = ARRAY_SIZE(debugfs_regs);
>  	dw_edma_debugfs_create_x32(debugfs_regs, nr_entries, regs_dir);
> @@ -253,8 +246,6 @@ static void dw_edma_debugfs_regs_rd(struct dentry *dir)
>  		snprintf(name, sizeof(name), "%s:%d", CHANNEL_STR, i);
>  
>  		ch_dir = debugfs_create_dir(name, regs_dir);
> -		if (!ch_dir)
> -			return;
>  
>  		dw_edma_debugfs_regs_ch(&regs->type.unroll.ch[i].rd, ch_dir);
>  
> @@ -273,8 +264,6 @@ static void dw_edma_debugfs_regs(void)
>  	int nr_entries;
>  
>  	regs_dir = debugfs_create_dir(REGISTERS_STR, dw->debugfs);
> -	if (!regs_dir)
> -		return;
>  
>  	nr_entries = ARRAY_SIZE(debugfs_regs);
>  	dw_edma_debugfs_create_x32(debugfs_regs, nr_entries, regs_dir);
> @@ -285,6 +274,9 @@ static void dw_edma_debugfs_regs(void)
>  
>  void dw_edma_v0_debugfs_on(struct dw_edma_chip *chip)
>  {
> +	if (!debugfs_initialized())
> +		return;
> +
>  	dw = chip->dw;
>  	if (!dw)
>  		return;
> @@ -294,8 +286,6 @@ void dw_edma_v0_debugfs_on(struct dw_edma_chip *chip)
>  		return;
>  
>  	dw->debugfs = debugfs_create_dir(dw->name, NULL);
> -	if (!dw->debugfs)
> -		return;
>  
>  	debugfs_create_u32("mf", 0444, dw->debugfs, &dw->chip->mf);
>  	debugfs_create_u16("wr_ch_cnt", 0444, dw->debugfs, &dw->wr_ch_cnt);
> -- 
> 2.35.1
>