Most serial drivers do this, see drivers/tty/serial for a 
number of examples, or drivers/serial on older kernels.

Thanks, will check it.

That would depend on your hardware. The only important part is 
that you make sure you can send out data at any time. If 
i2c_master_send() causes accesses to your buffer after 
returning, there has to be an i2c method of making sure that 
it has completed.

If the usleep_range is trying to synchronize between the NFC 
and the I2C chip, you must wait for a notication from the NFC 
hardware that it's done.

No, it's simply there as I have been faceing i2c write error while I do two consecutive writes.
The second fails now and then. That's seems to be a chip issue. I will try to investigate this issue.

quoted

What's more, I guess the i2c_master_send  is a synchronous call and 
when it returnes we know it flushed data. Right?

If i2c_master_send is synchronous, you might not need the 
usleep_range() at all. Removing that call would be entirely reasonable.

Will see how to approach that.

/Waldek--
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