67 lines
2.5 KiB
Plaintext
67 lines
2.5 KiB
Plaintext
SD and MMC Block Device Attributes
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==================================
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These attributes are defined for the block devices associated with the
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SD or MMC device.
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The following attributes are read/write.
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force_ro Enforce read-only access even if write protect switch is off.
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SD and MMC Device Attributes
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============================
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All attributes are read-only.
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cid Card Identifaction Register
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csd Card Specific Data Register
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scr SD Card Configuration Register (SD only)
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date Manufacturing Date (from CID Register)
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fwrev Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
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hwrev Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
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manfid Manufacturer ID (from CID Register)
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name Product Name (from CID Register)
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oemid OEM/Application ID (from CID Register)
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serial Product Serial Number (from CID Register)
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erase_size Erase group size
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preferred_erase_size Preferred erase size
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Note on Erase Size and Preferred Erase Size:
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"erase_size" is the minimum size, in bytes, of an erase
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operation. For MMC, "erase_size" is the erase group size
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reported by the card. Note that "erase_size" does not apply
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to trim or secure trim operations where the minimum size is
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always one 512 byte sector. For SD, "erase_size" is 512
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if the card is block-addressed, 0 otherwise.
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SD/MMC cards can erase an arbitrarily large area up to and
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including the whole card. When erasing a large area it may
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be desirable to do it in smaller chunks for three reasons:
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1. A single erase command will make all other I/O on
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the card wait. This is not a problem if the whole card
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is being erased, but erasing one partition will make
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I/O for another partition on the same card wait for the
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duration of the erase - which could be a several
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minutes.
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2. To be able to inform the user of erase progress.
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3. The erase timeout becomes too large to be very
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useful. Because the erase timeout contains a margin
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which is multiplied by the size of the erase area,
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the value can end up being several minutes for large
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areas.
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"erase_size" is not the most efficient unit to erase
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(especially for SD where it is just one sector),
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hence "preferred_erase_size" provides a good chunk
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size for erasing large areas.
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For MMC, "preferred_erase_size" is the high-capacity
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erase size if a card specifies one, otherwise it is
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based on the capacity of the card.
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For SD, "preferred_erase_size" is the allocation unit
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size specified by the card.
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"preferred_erase_size" is in bytes.
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