Documentation/mmc/mmc-dev-attrs.txt

   1 SD and MMC Block Device Attributes
   2 ==================================
   3
   4 These attributes are defined for the block devices associated with the
   5 SD or MMC device.
   6
   7 The following attributes are read/write.
   8
   9         force_ro                Enforce read-only access even if write protect switch is off.
  10
  11 SD and MMC Device Attributes
  12 ============================
  13
  14 All attributes are read-only.
  15
  16         cid                     Card Identifaction Register
  17         csd                     Card Specific Data Register
  18         scr                     SD Card Configuration Register (SD only)
  19         date                    Manufacturing Date (from CID Register)
  20         fwrev                   Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
  21         hwrev                   Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
  22         manfid                  Manufacturer ID (from CID Register)
  23         name                    Product Name (from CID Register)
  24         oemid                   OEM/Application ID (from CID Register)
  25         prv                     Product Revision (from CID Register) (SD and MMCv4 only)
  26         serial                  Product Serial Number (from CID Register)
  27         erase_size              Erase group size
  28         preferred_erase_size    Preferred erase size
  29         raw_rpmb_size_mult      RPMB partition size
  30         rel_sectors             Reliable write sector count
  31         ocr                     Operation Conditions Register
  32         dsr                     Driver Stage Register
  33
  34 Note on Erase Size and Preferred Erase Size:
  35
  36         "erase_size" is the  minimum size, in bytes, of an erase
  37         operation.  For MMC, "erase_size" is the erase group size
  38         reported by the card.  Note that "erase_size" does not apply
  39         to trim or secure trim operations where the minimum size is
  40         always one 512 byte sector.  For SD, "erase_size" is 512
  41         if the card is block-addressed, 0 otherwise.
  42
  43         SD/MMC cards can erase an arbitrarily large area up to and
  44         including the whole card.  When erasing a large area it may
  45         be desirable to do it in smaller chunks for three reasons:
  46                 1. A single erase command will make all other I/O on
  47                 the card wait.  This is not a problem if the whole card
  48                 is being erased, but erasing one partition will make
  49                 I/O for another partition on the same card wait for the
  50                 duration of the erase - which could be a several
  51                 minutes.
  52                 2. To be able to inform the user of erase progress.
  53                 3. The erase timeout becomes too large to be very
  54                 useful.  Because the erase timeout contains a margin
  55                 which is multiplied by the size of the erase area,
  56                 the value can end up being several minutes for large
  57                 areas.
  58
  59         "erase_size" is not the most efficient unit to erase
  60         (especially for SD where it is just one sector),
  61         hence "preferred_erase_size" provides a good chunk
  62         size for erasing large areas.
  63
  64         For MMC, "preferred_erase_size" is the high-capacity
  65         erase size if a card specifies one, otherwise it is
  66         based on the capacity of the card.
  67
  68         For SD, "preferred_erase_size" is the allocation unit
  69         size specified by the card.
  70
  71         "preferred_erase_size" is in bytes.
  72
  73 Note on raw_rpmb_size_mult:
  74         "raw_rpmb_size_mult" is a mutliple of 128kB block.
  75         RPMB size in byte is calculated by using the following equation:
  76         RPMB partition size = 128kB x raw_rpmb_size_mult