linux-kernel - Re: [PATCH 13/15] PCI/ASPM: use permission-specific DEVICE

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Message-ID: <20161114214037.GE9868@bhelgaas-glaptop.roam.corp.google.com>
Date:   Mon, 14 Nov 2016 15:40:37 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Julia Lawall <Julia.Lawall@...6.fr>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        kernel-janitors@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/15] PCI/ASPM: use permission-specific DEVICE_ATTR
 variants

On Sat, Oct 29, 2016 at 09:37:07PM +0200, Julia Lawall wrote:
> Use DEVICE_ATTR_RW for read-write attributes.  This simplifies the
> source code, improves readbility, and reduces the chance of
> inconsistencies.
> 
> The semantic patch that makes this change is as follows:
> (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @rw@
> declarer name DEVICE_ATTR;
> identifier x,x_show,x_store;
> @@
> 
> DEVICE_ATTR(x, \(0644\|S_IRUGO|S_IWUSR\), x_show, x_store);
> 
> @script:ocaml@
> x << rw.x;
> x_show << rw.x_show;
> x_store << rw.x_store;
> @@
> 
> if not (x^"_show" = x_show && x^"_store" = x_store)
> then Coccilib.include_match false
> 
> @@
> declarer name DEVICE_ATTR_RW;
> identifier rw.x,rw.x_show,rw.x_store;
> @@
> 
> - DEVICE_ATTR(x, \(0644\|S_IRUGO|S_IWUSR\), x_show, x_store);
> + DEVICE_ATTR_RW(x);
> // </smpl>
> 
> Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

I applied this to pci/aspm to follow the herd, although it looks
pretty similar to the ill-fated "Replace numeric parameter like 0444
with macro" series (http://lwn.net/Articles/696229/).  Maybe this is
different because everybody except me knows what ATTR_RW means?  To
me, "0644" contained more information than "_RW" does.

I do certainly like the removal of the "_show" and "_store"
redundancy.

> ---
>  drivers/pci/pcie/aspm.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 0ec649d..3b14d9e 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -886,8 +886,8 @@ static ssize_t clk_ctl_store(struct device *dev,
>  	return n;
>  }
>  
> -static DEVICE_ATTR(link_state, 0644, link_state_show, link_state_store);
> -static DEVICE_ATTR(clk_ctl, 0644, clk_ctl_show, clk_ctl_store);
> +static DEVICE_ATTR_RW(link_state);
> +static DEVICE_ATTR_RW(clk_ctl);
>  
>  static char power_group[] = "power";
>  void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev)
>