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Documentation / fmc / fmc-write-eeprom.txt

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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 EST.

1	fmc-write-eeprom
2	================
4	This module is designed to load a binary file from /lib/firmware and to
5	write it to the internal EEPROM of the mezzanine card. This driver uses
6	the `busid' generic parameter.
8	Overwriting the EEPROM is not something you should do daily, and it is
9	expected to only happen during manufacturing. For this reason, the
10	module makes it unlikely for the random user to change a working EEPROM.
12	However, since the EEPROM may include application-specific information
13	other than the identification, later versions of this packages added
14	write-support through sysfs. See *note Accessing the EEPROM::.
16	To avoid damaging the EEPROM content, the module takes the following
17	measures:
19	   * It accepts a `file=' argument (within /lib/firmware) and if no
20	     such argument is received, it doesn't write anything to EEPROM
21	     (i.e. there is no default file name).
23	   * If the file name ends with `.bin' it is written verbatim starting
24	     at offset 0.
26	   * If the file name ends with `.tlv' it is interpreted as
27	     type-length-value (i.e., it allows writev(2)-like operation).
29	   * If the file name doesn't match any of the patterns above, it is
30	     ignored and no write is performed.
32	   * Only cards listed with `busid=' are written to. If no busid is
33	     specified, no programming is done (and the probe function of the
34	     driver will fail).
37	Each TLV tuple is formatted in this way: the header is 5 bytes,
38	followed by data. The first byte is `w' for write, the next two bytes
39	represent the address, in little-endian byte order, and the next two
40	represent the data length, in little-endian order. The length does not
41	include the header (it is the actual number of bytes to be written).
43	This is a real example: that writes 5 bytes at position 0x110:
45	        spusa.root# od -t x1 -Ax /lib/firmware/try.tlv
46	        000000 77 10 01 05 00 30 31 32 33 34
47	        00000a
48	        spusa.root# insmod /tmp/fmc-write-eeprom.ko busid=0x0200 file=try.tlv
49	        [19983.391498] spec 0000:03:00.0: write 5 bytes at 0x0110
50	        [19983.414615] spec 0000:03:00.0: write_eeprom: success
52	Please note that you'll most likely want to use SDBFS to build your
53	EEPROM image, at least if your mezzanines are being used in the White
54	Rabbit environment. For this reason the TLV format is not expected to
55	be used much and is not expected to be developed further.
57	If you want to try reflashing fake EEPROM devices, you can use the
58	fmc-fakedev.ko module (see *note fmc-fakedev::).  Whenever you change
59	the image starting at offset 0, it will deregister and register again
60	after two seconds.  Please note, however, that if fmc-write-eeprom is
61	still loaded, the system will associate it to the new device, which
62	will be reprogrammed and thus will be unloaded after two seconds.  The
63	following example removes the module after it reflashed fakedev the
64	first time.
66	     spusa.root# insmod fmc-fakedev.ko
67	        [   72.984733]  fake-fmc: Manufacturer: fake-vendor
68	        [   72.989434]  fake-fmc: Product name: fake-design-for-testing
69	        spusa.root# insmod fmc-write-eeprom.ko busid=0 file=fdelay-eeprom.bin; \
70	            rmmod fmc-write-eeprom
71	        [  130.874098]  fake-fmc: Matching a generic driver (no ID)
72	        [  130.887845]  fake-fmc: programming 6155 bytes
73	        [  130.894567]  fake-fmc: write_eeprom: success
74	        [  132.895794]  fake-fmc: Manufacturer: CERN
75	        [  132.899872]  fake-fmc: Product name: FmcDelay1ns4cha
78	Accessing the EEPROM
79	=====================
81	The bus creates a sysfs binary file called eeprom for each mezzanine it
82	knows about:
84	        spusa.root# cd /sys/bus/fmc/devices; ls -l */eeprom
85	        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcAdc100m14b4cha-0800/eeprom
86	        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDelay1ns4cha-0200/eeprom
87	        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDio5cha-0400/eeprom
89	Everybody can read the files and the superuser can also modify it, but
90	the operation may on the carrier driver, if the carrier is unable to
91	access the I2C bus.  For example, the spec driver can access the bus
92	only with its golden gateware: after a mezzanine driver reprogrammed
93	the FPGA with a custom circuit, the carrier is unable to access the
94	EEPROM and returns ENOTSUPP.
96	An alternative way to write the EEPROM is the mezzanine driver
97	fmc-write-eeprom (See *note fmc-write-eeprom::), but the procedure is
98	more complex.
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