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The FT260 controller does not return NACK when performing a big read (of multiple hid reports size) from a non-existing device or from the device responding with NACK when it is not ready to serve the request. However, it responds correctly with NACK to a read of up to a single hid report size. To overcome this issue, we split the muli-report read request into a read of a single HID report of 60 bytes size and a multi-report read. Big read of 256 bytes with first read of 60 bytes: $ sudo ./i2cperf -d 2 -o 2 -s 256 -r 0-0xff 1 0x50 -S [ +5.633280] ft260_i2c_write_read: off 0x0 rlen 255 wlen 2 [ +0.000006] ft260_i2c_write: rep 0xd0 addr 0x50 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0 [ +0.013205] ft260_xfer_status: bus_status 0x20, clock 100 [ +0.000007] ft260_i2c_read: rep 0xc2 addr 0x50 len 255 rlen 60 flag 0x3 [ +0.010932] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.004733] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.000006] ft260_i2c_read: rep 0xc2 addr 0x50 len 195 rlen 128 flag 0x0 [ +0.012572] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.005789] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.003189] ft260_raw_event: i2c resp: rep 0xd1 len 8 [ +0.004092] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.000010] ft260_i2c_read: rep 0xc2 addr 0x50 len 67 rlen 67 flag 0x4 [ +0.011688] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.004700] ft260_raw_event: i2c resp: rep 0xd1 len 7 [ +0.004858] ft260_xfer_status: bus_status 0x20, clock 100 Read from non-existing device at address 8. The first 60 read responded with NACK. $ sudo ./i2cperf -d 2 -o 2 -s 256 -r 0-0xff 1 0x8 -S [Oct19 15:37] ft260_i2c_write_read: off 0x0 rlen 255 wlen 2 [ +0.000007] ft260_i2c_write: rep 0xd0 addr 0x8 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0 [ +0.022820] ft260_xfer_status: bus_status 0x20, clock 100 [ +0.000007] ft260_i2c_read: rep 0xc2 addr 0x8 len 255 rlen 60 flag 0x3 [ +0.010658] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.005965] ft260_xfer_status: bus_status 0x46, clock 100 <-- NACK [ +0.000009] ft260 0003:0403:6030.0004: i2c bus error: 0x46 [ +0.007784] ft260_i2c_reset: done Co-developed-by: Enrik Berkhan <Enrik.Berkhan@inka.de> Signed-off-by: Enrik Berkhan <Enrik.Berkhan@inka.de> Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.