Re: [PATCH] mmc: add device class attribute for ext_csd

[Adrian Hunter <adrian.hunter@nokia.com>]

Ghorai, Sukumar wrote:
> 
>> -----Original Message-----
>> From: Adrian Hunter [mailto:adrian.hunter@nokia.com]
>> Sent: Monday, July 26, 2010 6:13 PM
>> To: Ghorai, Sukumar
>> Cc: linux-mmc@vger.kernel.org; Andrew Morton
>> Subject: Re: [PATCH] mmc: add device class attribute for ext_csd
>>
>> Ghorai, Sukumar wrote:
>>> All,
>>> EXT_CSD is 512byte information (read using CMD8) for the MMC (eMMC)
>> device.
>>> And for the latest and upcoming specification, ext_csd are much relevant
>> then past.
>>> So please let me know your idea to add and get the same ext_csd as MMC
>> device attribute. This is the same way currently available for csd, cid,
>> src, etc.
>>> (# cat /sys/class/mmc_host/mmc1/mmc1\:0001/ext_csd)
>> Some of the values in Extended CSD can change so storing
>> it could cause incorrect values to be reported.
> [Ghorai] I was thinking to get the original value as reference, such that we know that host is capable for maximum negotiation, like 8-bit, DDR mode, voltage, etc.
> 1. Is there any other way to get the original value supported by card?
> 2. If yes, is it worth full to do?

If it is for debugging, would a debug prints do instead e.g.

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 89f7a25..cba87b0 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -249,6 +249,9 @@ static int mmc_read_ext_csd(struct mmc_card *card)
                                        1 << ext_csd[EXT_CSD_S_A_TIMEOUT];
        }
 
+       pr_debug("%s: initial ext_csd bus width code %02x",
+                mmc_hostname(host), ext_csd[EXT_CSD_BUS_WIDTH]);
+
 out:
        kfree(ext_csd);
 


> 
>> Note that Extended CSD is available via debugfs
>> e.g. for device mmc0:0001 with debugfs mounted on /sys/kernel/debug
>>
>>     cat /sys/kernel/debug/mmc0/mmc0\:0001/ext_csd
> [Ghorai] Thanks. I got it.
> 
> <<snip>>
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