linux-kernel - Re: [PATCH] fw_cfg: use __ATTR_RO

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Message-ID: <20190227053319.GB5449@richard>
Date:   Wed, 27 Feb 2019 13:33:19 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>, qemu-devel@...gnu.org,
        linux-kernel@...r.kernel.org, somlo@....edu
Subject: Re: [PATCH] fw_cfg: use __ATTR_RO_MODE to define rev sysfs

On Tue, Feb 26, 2019 at 11:10:06AM -0500, Michael S. Tsirkin wrote:
>On Tue, Feb 26, 2019 at 03:31:59PM +0800, Wei Yang wrote:
>> Leverage __ATTR_RO_MODE to define rev sysfs instead of using open code
>> to define the attribute.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
>> ---
>>  drivers/firmware/qemu_fw_cfg.c | 13 ++++---------
>>  1 file changed, 4 insertions(+), 9 deletions(-)
>> 
>> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
>> index 039e0f91dba8..a1293cbd7adb 100644
>> --- a/drivers/firmware/qemu_fw_cfg.c
>> +++ b/drivers/firmware/qemu_fw_cfg.c
>> @@ -296,18 +296,13 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
>>  	return 0;
>>  }
>>  
>> -static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
>> +static ssize_t fw_cfg_rev_show(struct kobject *k, struct kobj_attribute *a,
>> +			       char *buf)
>>  {
>>  	return sprintf(buf, "%u\n", fw_cfg_rev);
>>  }
>> -
>> -static const struct {
>> -	struct attribute attr;
>> -	ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
>> -} fw_cfg_rev_attr = {
>> -	.attr = { .name = "rev", .mode = S_IRUSR },
>> -	.show = fw_cfg_showrev,
>> -};
>> +static const struct kobj_attribute fw_cfg_rev_attr =
>> +	__ATTR_RO_MODE(fw_cfg_rev, 0400);
>>  
>>  /* fw_cfg_sysfs_entry type */
>>  struct fw_cfg_sysfs_entry {
>
>
>Looks like this will change the name from "rev" to "fw_cfg_rev".
>That's a userspace visible change which we should not do lightly.

You are right, I should keep the interface untouched.

To keep it user un-visible, we could change like below:

-       __ATTR_RO(fw_cfg_rev);
+       __ATTR_RO(rev);

Is this better for you?

>> -- 
>> 2.19.1

-- 
Wei Yang
Help you, Help me