linux-kernel - Re: [PATCH -next] memory: Convert to DEFINE_SHOW

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Message-ID: <55762551-4f14-b7f8-c2ae-e93e75ef3299@huawei.com>
Date:   Mon, 20 Jul 2020 10:02:19 +0800
From:   miaoqinglang <miaoqinglang@...wei.com>
To:     Pavel Machek <pavel@...x.de>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        <linux-bcache@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] memory: Convert to DEFINE_SHOW_ATTRIBUTE



在 2020/7/18 5:14, Pavel Machek 写道:
> On Thu 2020-07-16 17:03:03, Qinglang Miao wrote:
>> From: Yongqiang Liu <liuyongqiang13@...wei.com>
>>
>> Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code.
>>
>> Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
>> ---
>>   drivers/memory/emif.c               | 22 ++--------------------
>>   drivers/memory/tegra/tegra124-emc.c | 14 +-------------
>>   2 files changed, 3 insertions(+), 33 deletions(-)
>>
>> diff --git a/drivers/memory/emif.c b/drivers/memory/emif.c
>> index 58a82eea5..aab8ddad7 100644
>> --- a/drivers/memory/emif.c
>> +++ b/drivers/memory/emif.c
>> @@ -131,16 +131,7 @@ static int emif_regdump_show(struct seq_file *s, void *unused)
>>   	return 0;
>>   }
>>   
>> -static int emif_regdump_open(struct inode *inode, struct file *file)
>> -{
>> -	return single_open(file, emif_regdump_show, inode->i_private);
>> -}
>> -
>> -static const struct file_operations emif_regdump_fops = {
>> -	.open			= emif_regdump_open,
>> -	.read_iter			= seq_read_iter,
>> -	.release		= single_release,
>> -};
>> +DEFINE_SHOW_ATTRIBUTE(emif_regdump);
> 
> This is not equivalent (and I guess changelog should mention that).
> 
> Along with other changes, we get:
> 
>          .owner          = THIS_MODULE,
>          .llseek         = seq_lseek,
> 
> . Is that okay thing to add?
> 									Pavel
> 
Hi Pavel,

You're right, I should of mention it in changelog.

There's no impact theoretically with these two changes. Here's my thoughs:

1. The llseek method is used to change the current read/write position 
in a file which can be ignored if you don't use it.
2. The owner is not even a method. Instead, it is a pointer to the 
module that “owns” this structure; it is used by the kernel to maintain 
the module's usage count which I believe can be ignored.

If you don't mind I can send a new patch with more specific changelog.

Thanks.

Qinglang

.