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-rw-r--r--Documentation/00-INDEX2
-rw-r--r--Documentation/mmc/00-INDEX4
-rw-r--r--Documentation/mmc/mmc-dev-attrs.txt56
3 files changed, 62 insertions, 0 deletions
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 9e642c5bf52..8dfc6708a25 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -232,6 +232,8 @@ memory.txt
- info on typical Linux memory problems.
mips/
- directory with info about Linux on MIPS architecture.
+mmc/
+ - directory with info about the MMC subsystem
mono.txt
- how to execute Mono-based .NET binaries with the help of BINFMT_MISC.
mutex-design.txt
diff --git a/Documentation/mmc/00-INDEX b/Documentation/mmc/00-INDEX
new file mode 100644
index 00000000000..fca586f5b85
--- /dev/null
+++ b/Documentation/mmc/00-INDEX
@@ -0,0 +1,4 @@
+00-INDEX
+ - this file
+mmc-dev-attrs.txt
+ - info on SD and MMC device attributes
diff --git a/Documentation/mmc/mmc-dev-attrs.txt b/Documentation/mmc/mmc-dev-attrs.txt
new file mode 100644
index 00000000000..ff2bd685bce
--- /dev/null
+++ b/Documentation/mmc/mmc-dev-attrs.txt
@@ -0,0 +1,56 @@
+SD and MMC Device Attributes
+============================
+
+All attributes are read-only.
+
+ cid Card Identifaction Register
+ csd Card Specific Data Register
+ scr SD Card Configuration Register (SD only)
+ date Manufacturing Date (from CID Register)
+ fwrev Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
+ hwrev Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
+ manfid Manufacturer ID (from CID Register)
+ name Product Name (from CID Register)
+ oemid OEM/Application ID (from CID Register)
+ serial Product Serial Number (from CID Register)
+ erase_size Erase group size
+ preferred_erase_size Preferred erase size
+
+Note on Erase Size and Preferred Erase Size:
+
+ "erase_size" is the minimum size, in bytes, of an erase
+ operation. For MMC, "erase_size" is the erase group size
+ reported by the card. Note that "erase_size" does not apply
+ to trim or secure trim operations where the minimum size is
+ always one 512 byte sector. For SD, "erase_size" is 512
+ if the card is block-addressed, 0 otherwise.
+
+ SD/MMC cards can erase an arbitrarily large area up to and
+ including the whole card. When erasing a large area it may
+ be desirable to do it in smaller chunks for three reasons:
+ 1. A single erase command will make all other I/O on
+ the card wait. This is not a problem if the whole card
+ is being erased, but erasing one partition will make
+ I/O for another partition on the same card wait for the
+ duration of the erase - which could be a several
+ minutes.
+ 2. To be able to inform the user of erase progress.
+ 3. The erase timeout becomes too large to be very
+ useful. Because the erase timeout contains a margin
+ which is multiplied by the size of the erase area,
+ the value can end up being several minutes for large
+ areas.
+
+ "erase_size" is not the most efficient unit to erase
+ (especially for SD where it is just one sector),
+ hence "preferred_erase_size" provides a good chunk
+ size for erasing large areas.
+
+ For MMC, "preferred_erase_size" is the high-capacity
+ erase size if a card specifies one, otherwise it is
+ based on the capacity of the card.
+
+ For SD, "preferred_erase_size" is the allocation unit
+ size specified by the card.
+
+ "preferred_erase_size" is in bytes.