linux-kernel - Re: [BUG] MMC/SD: SDHC card capacity not correct

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Date:	Tue, 13 Jan 2009 16:00:21 +0800
From:	yi li <liyi.dev@...il.com>
To:	Pierre Ossman <drzeus-mmc@...eus.cx>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [BUG] MMC/SD: SDHC card capacity not correct

On Mon, Jan 12, 2009 at 11:20 PM, Pierre Ossman <drzeus-mmc@...eus.cx> wrote:
>
> Odd. Is the entire device accessible? (I.e. is it just a printk
> problem?)
>

It is a printk problem.

> Could you give me a dmesg dump with MMC_DEBUG turned on in Kconfig?
>

I did debug on my side (I think it is more easy to reproduce here :-)
).  The issue is in mmc/card/block.c: mmc_block_probe().

"string_get_size(get_capacity(md->disk) << 9, STRING_UNITS_2,
 			cap_str, sizeof(cap_str));
"
get_capacity() returns a type "sector_t" value, since I am working on
a 32-bit processor (Analog Devices BF537),
and I did not enable CONFIG_LBD, "sector_t" is actually a 32-bit
"unsigned long".  So  "get_capacity(md->disk) << 9" loses the MSB.

I can think of two fixes:

1. Set CONFIG_LBD
2. Fix like this:
--- card/block.c	2009-01-13 15:56:05.000000000 +0800
+++ card/block.c.new	2009-01-13 15:53:45.000000000 +0800
@@ -514,7 +514,7 @@ static int mmc_blk_probe(struct mmc_card
 	if (err)
 		goto out;

-	string_get_size(get_capacity(md->disk) << 9, STRING_UNITS_2,
+	string_get_size((u64)get_capacity(md->disk) << 9, STRING_UNITS_2,
 			cap_str, sizeof(cap_str));
 	printk(KERN_INFO "%s: %s %s %s %s\n",
 		md->disk->disk_name, mmc_card_id(card), mmc_card_name(card),

I prefer the second fix, what do you think?

Regards,

-Li Yi
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