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Documentation / mmc / mmc-dev-attrs.txt




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Based on kernel version 4.8. Page generated on 2016-10-06 23:18 EST.

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
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