linux-kernel - Re: [PATCH] mmc: check EXT_CSD_PARTITION_SETTING

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Message-ID: <53ECB95F.2030207@neotion.com>
Date:	Thu, 14 Aug 2014 15:27:59 +0200
From:	Grégory Soutadé <gsoutade@...tion.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
CC:	Chris Ball <chris@...ntf.net>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: check EXT_CSD_PARTITION_SETTING_COMPLETED before
 creating partitions

Le 14/08/2014 13:46, Ulf Hansson a écrit :
> On 13 August 2014 11:20, Grégory Soutadé <gsoutade@...tion.com> wrote:
>> Le 13/08/2014 10:36, Ulf Hansson a écrit :
>>> On 17 July 2014 16:57, Grégory Soutadé <gsoutade@...tion.com> wrote:
>>>> Create MMC general purpose partitions only if
>>>> EXT_CSD_PARTITION_SETTING_COMPLETED bit is set.
>>>> Some tools may set general purpose partition size(s) but fail or stop
>>>> without finalize.
>>>> Another case is to set invalid partition size(s).
>>>>
>>>> Signed-off-by: Grégory Soutadé <gsoutade@...tion.com>
>>>> ---
>>>>  drivers/mmc/core/mmc.c  |   15 +++++++++++----
>>>>  include/linux/mmc/mmc.h |    2 ++
>>>>  2 files changed, 13 insertions(+), 4 deletions(-)
>>>>
>>>> From commit b6603fe574af289dbe9eb9fb4c540bca04f5a053 in master linux tree.
>>>>
>>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>>> index 793c6f7..b9fe211 100644
>>>> --- a/drivers/mmc/core/mmc.c
>>>> +++ b/drivers/mmc/core/mmc.c
>>>> @@ -471,10 +471,17 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
>>>>                                 ext_csd[EXT_CSD_GP_SIZE_MULT + idx * 3];
>>>>                                 part_size *= (size_t)(hc_erase_grp_sz *
>>>>                                         hc_wp_grp_sz);
>>>> -                               mmc_part_add(card, part_size << 19,
>>>> -                                       EXT_CSD_PART_CONFIG_ACC_GP0 + idx,
>>>> -                                       "gp%d", idx, false,
>>>> -                                       MMC_BLK_DATA_AREA_GP);
>>>> +                               if (ext_csd[EXT_CSD_PARTITION_SETTING_COMPLETED] &
>>>> +                               EXT_CSD_PART_SETTING_COMPLETED) {
>>>
>>> Some minor comments here.
>>>
>>> I think you could move this if statement up and into the previous "if"
>>> where we check for "ext_csd[EXT_CSD_PARTITION_SUPPORT] &
>>> EXT_CSD_PART_SUPPORT_PART_EN".
>>>
>>> Additionally, please run checkpatch.
>>>
>>> Kind regards
>>> Uffe
>>
>> Hello,
>>
>> I didn't put the if statement above to warn user in case of bad partitioning.
>> I don't want the kernel to silently ignore this error.
> 
> Fair enough.
> 
> Still I am wondering whether hc_erase_grp_sz, hc_wp_grp_sz and
> enhanced_area_en should be updated if
> EXT_CSD_PARTITION_SETTING_COMPLETED isn't set.  That's the case in
> your patch.

I was focused on partitions and I didn't pay attention on enhanced area.

JEDEC says that partitioning implies :
* Configure general purpose partitions attributes and sizes
* Configure enhanced user area offset, attributes and size

and finally set EXT_CSD_PARTITION_SETTING_COMPLETED.

Thus these two parts must checks for setting completed before
computing values.

Plus, "enhanced_area_en" attribute is set whether or not there is an
enhanced area defined. I looked at the code, and the only usage of it
is to set EXT_CSD_ERASE_GROUP_DEF and compute erase size again.
I suggest using "partition_setting_completed" identifier which is common
to the two functions and requires EXT_CSD_ERASE_GROUP_DEF to be set.

If you're ok with that, I'll submit another patch.


Best regards
Grégory Soutadé

> 
>>
>> checkpatch has been run before sending this patch, I know there are two lines
>> with two extra characters, but names used here are quite long. I hope it will
>> not block upstream inclusion.
> 
> The mmc_read_ext_csd() is not one of the nicest piece of code, but for
> sure we should not move on making it worse. If you need to move code
> into separate function to prevent checkpatch warnings, please do so.
> 
> Kind regards
> Uffe
> 


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