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SubjectRe: [PATCHv6 3/3] mmc_test: collect data and show it via sysfs by demand
On Tue, Sep 07, 2010 at 03:27:53PM -0700, Andrew Morton wrote:
> So what we end up with is extremely thin. Something about adding
> something to sysfs.
> This is not enough! You're proposing an addition to the kernel->user
> ABI. Please fully describe this interface so that we can understand
> and review it. What are the names of these sysfs files? What do they
> do? Provide us with example output in the changelog so we can see for
> ourselves.

Hoping Andy doesn't mind me jumping in, here's an attempt at a better


Prior to this patch, the "test" file under each card's sysfs node was
write-only, and results were obtained by looking at dmesg. This patch
improves programmatic access to the test results, making them available
by reading back from the same "test" file:

[root@host mmc0:e624]# echo 6 > test
[root@host mmc0:e624]# cat test
Test 6: 2

> Please consider documenting the thing in a permanent documentation
> file. (I don't believe that Documentation/ABI/ is appropriate, given
> mmc_test's scope).

I think we should do this by modifying the Kconfig text as well:

diff --git a/drivers/mmc/card/Kconfig b/drivers/mmc/card/Kconfig
index 3f2a912..ddd7e42 100644
--- a/drivers/mmc/card/Kconfig
+++ b/drivers/mmc/card/Kconfig
@@ -45,8 +45,9 @@ config MMC_TEST
Development driver that performs a series of reads and writes
to a memory card in order to expose certain well known bugs
in host controllers. The tests are executed by writing to the
- "test" file in sysfs under each card. Note that whatever is
- on your card will be overwritten by these tests.
+ "test" file in sysfs under each card, and results can be read
+ back from the same file. Note that whatever is on your card
+ will be overwritten by these tests.

This driver is only of interest to those developing or
testing a host driver. Most people should say N here.
Separately, Andy, I think we should translate the general result return
code for the user, i.e. print OK/FAIL/UNSUP_HOST/UNSUP_CARD for return
values 0-3. Would you mind adding that? (Unfortunately, it invalidates
the usage example I just gave above, so that should change too..)


Chris Ball <> <>
One Laptop Per Child

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