Writable SD-Card

m.ende · Oct 15th 2013

Hi,

after successfully mounting the sd-card I've realized that it's mounted read-only.

I've tried to mount it rw but that didn't worked.... (Physical write protection is off)

Code

mount -t vfat -o rw /dev/mmcblk0p1 /sdcard/

The result is the same as when I didn't specify the options:

Code

/dev/mmcblk0p1 on /sdcard type vfat (ro,relatime,fmask=0000,dmask=0000,allow_utime=0022,codepage=cp437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

What do I have to do when I'd like to write on the card?? Is there another hidden switch?!?

Thanks

Marc

ForTest · Oct 15th 2013

/dev/mmcblk0p1 on /sdcard type vfat (ro,relatime,fmask=0000,dmask=0000,allow_utime=0022,codepage=cp437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

try

Code

mount -o remount,rw /sdcard

fs-support_HK · Oct 15th 2013

Thanks for pointing this out. Yes, apparently Samsung has implemented this write-protect detection bit wrongly in the hardware. The following patch should fix this in software.

Diff

Write-protect detection is inverted on Samsung CPUs. In fact there
is no write-protect detection at all on these CPUs, but this bit is
fixed to High, which is by definition write-protected. But we want
write-enabled by default. So use the inverted value of this bit.
---
drivers/mmc/host/sdhci-s3c.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index c9ce748..4f3442c 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -520,6 +520,12 @@ static int __devinit sdhci_s3c_probe(struct platform_device *pdev)
* SDHCI block, or a missing configuration that needs to be set. */
host->quirks |= SDHCI_QUIRK_NO_BUSY_IRQ;
+ /* Write-protect detection is inverted on Samsung CPUs. In fact there
+ is no write-protect detection at all on these CPUs, but this bit is
+ fixed to High, which is by definition write-protected. But we want
+ write-enabled by default. So use the inverted value of this bit. */
+ host->quirks |= SDHCI_QUIRK_INVERTED_WRITE_PROTECT;
+
if (pdata->cd_type == S3C_SDHCI_CD_NONE ||
pdata->cd_type == S3C_SDHCI_CD_PERMANENT)
host->quirks |= SDHCI_QUIRK_BROKEN_CARD_DETECTION;

Display More

The patch is also attached to this posting for download. Then go to the top level directory of the Linux kernel source and apply the patch with the following command

Code

patch -p1 < Invert-SD-Card-write-protect-detection-on-Samsung-CPUs.patch

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