[PATCH 1/2] libmtd: Add support to access OOB available size

[David Oberhollenzer]

On 04/09/2018 10:45 AM, xiaolei li wrote:
> On Mon, 2018-04-09 at 10:37 +0200, Boris Brezillon wrote:
>> On Mon, 9 Apr 2018 16:33:11 +0800
>> xiaolei li <xiaolei.li at mediatek.com> wrote:
>>
>>> Hi Boris,
>>>
>>> On Mon, 2018-04-09 at 09:35 +0200, Boris Brezillon wrote:
>>>> On Mon, 9 Apr 2018 15:25:39 +0800
>>>> xiaolei li <xiaolei.li at mediatek.com> wrote:
>>>>   
>>>>> Hi David,
>>>>>
>>>>> On Mon, 2018-04-09 at 08:58 +0200, David Oberhollenzer wrote:  
>>>>>> Hi,
>>>>>>
>>>>>> On 04/09/2018 05:10 AM, Xiaolei Li wrote:    
>>>>>>> @@ -769,6 +774,8 @@ int mtd_get_dev_info1(libmtd_t desc, int mtd_num, struct mtd_dev_info *mtd)
>>>>>>>  		return -1;
>>>>>>>  	if (dev_read_pos_int(lib->mtd_oob_size, mtd_num, &mtd->oob_size))
>>>>>>>  		return -1;
>>>>>>> +	if (dev_read_pos_int(lib->mtd_oobavail, mtd_num, &mtd->oobavail))
>>>>>>> +		return -1;
>>>>>>>  	if (dev_read_pos_int(lib->mtd_region_cnt, mtd_num, &mtd->region_cnt))
>>>>>>>  		return -1;
>>>>>>>  	if (dev_read_hex_int(lib->mtd_flags, mtd_num, &ret))    
>>>>>>
>>>>>> I'm not sure if it is a good idea to do a hard fail here, since this
>>>>>> depends on a recent change to the kernel.
>>>>>>
>>>>>> It might be preferable to catch and handle ENOENT, otherwise the next
>>>>>> release of mtd-utils will only work on the next kernel release onward.
>>>>>>     
>>>>> Yes, it is. The hard fail return here seems not good.
>>>>>   
>>>>>> Maybe mtd_oobavail could to be set to some reasonable default that
>>>>>> retains the current behaviour on "older" kernels?
>>>>>>     
>>>>> What about setting 0 as default?  
>>>>
>>>> I didn't look closely at the code yet, but shouldn't we do something
>>>> like:
>>>>
>>>> 1/ search for oobavail file in sysfs
>>>> 2/ if it's not there use the GETOOBSEL or GETECCLAYOUT ioctl to get
>>>>    this information  
>>> MEMGETOOBSEL and GETECCLAYOUT are obsoleted. Should we keep using them
>>> here?
>>
>> Yes we should, otherwise old kernels won't work with new versions of
>> mtd-utils.
> OK.
> 
> @David, do you have other comments? If no, I will work for next patch to
> add GETOOBSEL/GETECCLAYOUT ioctl support as Boris's suggestion.
> 
> 

If a fallback to GETOOBSEL/GETECCLAYOUT works, I'm fine with that.

Thanks,

David