esp32_i2c: allow to read many bytes (QEMU-95)

[knw1]

Hi There!

The pull request provides a fix that solves a problem of reading a few bytes at once (as one transaction) from an emulated i2c device

I encountered the problem during using the example "i2c_tools".
Consider the following i2c-tools cmd:

i2c-tools> i2cget -c 0x48 -r 0x00 -l 0x05
0x19 0xee 0xee 0xee 0x00 
i2c-tools> 

There is an error on stdout/stderr of the qemu during performing above cmd:

qemu-system-xtensa: esp32_i2c: read I2C FIFO while it is empty
qemu-system-xtensa: esp32_i2c: read I2C FIFO while it is empty
qemu-system-xtensa: esp32_i2c: read I2C FIFO while it is empty

Response after applying my changes

i2c-tools> i2cget -c 0x48 -r 0x00 -l 0x05
0x19 0x00 0xff 0xff 0xff 
i2c-tools> 

No error on QEMU stdout/stderr. Got expected result, emulated TMP105 returns 0xff when i2c master wants to read more than two bytes

If you need more info, let me know.

Best regards,
Karol

[knw1]

ping

[igrr]

Thanks a lot for the fix, and sorry I have overlooked your PR when doing the recent rebase to v7.2.0. One small comment, which I can also apply myself when cherry-picking your commit, if you agree.

[knw1]

Corrected according to your suggestion :)

[knw1]

Thanks a lot for the fix, and sorry I have overlooked your PR when doing the recent rebase to v7.2.0. One small comment, which I can also apply myself when cherry-picking your commit, if you agree.

I prepared a correction and squashed the commits so there is only one commit.

[igrr]

Cherry-picked as db73e5e, thank you for the fix!