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