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Documentation / mmc / mmc-dev-attrs.txt




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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 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 Identification 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		cmdq_en			Command Queue enabled: 1 => enabled, 0 => not enabled
34	
35	Note on Erase Size and Preferred Erase Size:
36	
37		"erase_size" is the  minimum size, in bytes, of an erase
38		operation.  For MMC, "erase_size" is the erase group size
39		reported by the card.  Note that "erase_size" does not apply
40		to trim or secure trim operations where the minimum size is
41		always one 512 byte sector.  For SD, "erase_size" is 512
42		if the card is block-addressed, 0 otherwise.
43	
44		SD/MMC cards can erase an arbitrarily large area up to and
45		including the whole card.  When erasing a large area it may
46		be desirable to do it in smaller chunks for three reasons:
47			1. A single erase command will make all other I/O on
48			the card wait.  This is not a problem if the whole card
49			is being erased, but erasing one partition will make
50			I/O for another partition on the same card wait for the
51			duration of the erase - which could be a several
52			minutes.
53			2. To be able to inform the user of erase progress.
54			3. The erase timeout becomes too large to be very
55			useful.  Because the erase timeout contains a margin
56			which is multiplied by the size of the erase area,
57			the value can end up being several minutes for large
58			areas.
59	
60		"erase_size" is not the most efficient unit to erase
61		(especially for SD where it is just one sector),
62		hence "preferred_erase_size" provides a good chunk
63		size for erasing large areas.
64	
65		For MMC, "preferred_erase_size" is the high-capacity
66		erase size if a card specifies one, otherwise it is
67		based on the capacity of the card.
68	
69		For SD, "preferred_erase_size" is the allocation unit
70		size specified by the card.
71	
72		"preferred_erase_size" is in bytes.
73	
74	Note on raw_rpmb_size_mult:
75		"raw_rpmb_size_mult" is a multiple of 128kB block.
76		RPMB size in byte is calculated by using the following equation:
77		RPMB partition size = 128kB x raw_rpmb_size_mult
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