Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 98 insertions, 0 deletions

diff --git a/Documentation/fmc/fmc-write-eeprom.txt b/Documentation/fmc/fmc-write-eeprom.txt
new file mode 100644
index 000000000..e0a971215
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+++ b/Documentation/fmc/fmc-write-eeprom.txt
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+fmc-write-eeprom
+================
+
+This module is designed to load a binary file from /lib/firmware and to
+write it to the internal EEPROM of the mezzanine card. This driver uses
+the `busid' generic parameter.
+
+Overwriting the EEPROM is not something you should do daily, and it is
+expected to only happen during manufacturing. For this reason, the
+module makes it unlikely for the random user to change a working EEPROM.
+
+However, since the EEPROM may include application-specific information
+other than the identification, later versions of this packages added
+write-support through sysfs. See *note Accessing the EEPROM::.
+
+To avoid damaging the EEPROM content, the module takes the following
+measures:
+
+   * It accepts a `file=' argument (within /lib/firmware) and if no
+     such argument is received, it doesn't write anything to EEPROM
+     (i.e. there is no default file name).
+
+   * If the file name ends with `.bin' it is written verbatim starting
+     at offset 0.
+
+   * If the file name ends with `.tlv' it is interpreted as
+     type-length-value (i.e., it allows writev(2)-like operation).
+
+   * If the file name doesn't match any of the patterns above, it is
+     ignored and no write is performed.
+
+   * Only cards listed with `busid=' are written to. If no busid is
+     specified, no programming is done (and the probe function of the
+     driver will fail).
+
+
+Each TLV tuple is formatted in this way: the header is 5 bytes,
+followed by data. The first byte is `w' for write, the next two bytes
+represent the address, in little-endian byte order, and the next two
+represent the data length, in little-endian order. The length does not
+include the header (it is the actual number of bytes to be written).
+
+This is a real example: that writes 5 bytes at position 0x110:
+
+        spusa.root# od -t x1 -Ax /lib/firmware/try.tlv
+        000000 77 10 01 05 00 30 31 32 33 34
+        00000a
+        spusa.root# insmod /tmp/fmc-write-eeprom.ko busid=0x0200 file=try.tlv
+        [19983.391498] spec 0000:03:00.0: write 5 bytes at 0x0110
+        [19983.414615] spec 0000:03:00.0: write_eeprom: success
+
+Please note that you'll most likely want to use SDBFS to build your
+EEPROM image, at least if your mezzanines are being used in the White
+Rabbit environment. For this reason the TLV format is not expected to
+be used much and is not expected to be developed further.
+
+If you want to try reflashing fake EEPROM devices, you can use the
+fmc-fakedev.ko module (see *note fmc-fakedev::).  Whenever you change
+the image starting at offset 0, it will deregister and register again
+after two seconds.  Please note, however, that if fmc-write-eeprom is
+still loaded, the system will associate it to the new device, which
+will be reprogrammed and thus will be unloaded after two seconds.  The
+following example removes the module after it reflashed fakedev the
+first time.
+
+     spusa.root# insmod fmc-fakedev.ko
+        [   72.984733]  fake-fmc: Manufacturer: fake-vendor
+        [   72.989434]  fake-fmc: Product name: fake-design-for-testing
+        spusa.root# insmod fmc-write-eeprom.ko busid=0 file=fdelay-eeprom.bin; \
+            rmmod fmc-write-eeprom
+        [  130.874098]  fake-fmc: Matching a generic driver (no ID)
+        [  130.887845]  fake-fmc: programming 6155 bytes
+        [  130.894567]  fake-fmc: write_eeprom: success
+        [  132.895794]  fake-fmc: Manufacturer: CERN
+        [  132.899872]  fake-fmc: Product name: FmcDelay1ns4cha
+
+
+Accessing the EEPROM
+=====================
+
+The bus creates a sysfs binary file called eeprom for each mezzanine it
+knows about:
+
+        spusa.root# cd /sys/bus/fmc/devices; ls -l */eeprom
+        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcAdc100m14b4cha-0800/eeprom
+        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDelay1ns4cha-0200/eeprom
+        -r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDio5cha-0400/eeprom
+
+Everybody can read the files and the superuser can also modify it, but
+the operation may on the carrier driver, if the carrier is unable to
+access the I2C bus.  For example, the spec driver can access the bus
+only with its golden gateware: after a mezzanine driver reprogrammed
+the FPGA with a custom circuit, the carrier is unable to access the
+EEPROM and returns ENOTSUPP.
+
+An alternative way to write the EEPROM is the mezzanine driver
+fmc-write-eeprom (See *note fmc-write-eeprom::), but the procedure is
+more complex.