Re: Kmod driver at iicbus. attach() and config_intrhook(9)

Alexander Mishin писал 2020-09-04 10:00:
> Ian Lepore писал 2020-09-03 18:48:
>> On Thu, 2020-09-03 at 15:02 +0400, Alexander Mishin wrote:
>>> Andriy Gapon писал 2020-09-03 11:29:
>>> > On 02/09/2020 01:18, John-Mark Gurney wrote:
>>> > > So my reading of the twsi driver is that it handles things correctly
>>> > > allowing devices pre-interrupts to attach, and using interrupts for
>>> > > transfers post-cold.
>>> >
>>> > I just want to note that twsi uses _completely_ different code for
>>> > polled and
>>> > interrupt modes.  So, while either mode should be active at correct
>>> > times, I
>>> > cannot certify that the polled mode works correctly for all transfer
>>> > types.
>>> > I haven't reviewed the polled mode code.
>>> 
>>> This adds some more light on my question.
>>> 
>>> As a result:
>>> For twsi I use iicbb_transfer() (as Emmanuel Vadot recommended to
>>> someone on the mailing list).
>>> It is definitely not works for my driver, until interrupts went 
>>> enabled.
>>> But it works perfectly well with the config_intrhook().
>>> 
>>> I have never tried iicbus_write() at boot time yet, but I think I'll
>>> try, just to know for the future.
>>> 
>>> Thanks
>>> 
>> All i2c slave drivers should be using iicbus_transfer_excl() or the
>> iicdev_readfrom()/iicdev_writeto() helper functions.  The only time to
>> use iicbus_transfer() directly is when you need to conduct a dialog
>> with one or more slaves using multiple transactions and it's important
>> to keep the bus locked across the entire series of transactions for
>> some reason (meaning you must handle the acquire/release bus stuff
>> yourself).  There is virtually never a reason to call the low-level
>> start/stop/read/write functions directly.
>> 
>> It's a pity that this stuff is so horribly documented.  It has evolved
>> extensively over the years, not always in good ways, and documentation
>> and examples either don't exist or haven't kept up.
>> 
>> Bottom line: if the twsi driver has the config_intrhook logic in it
>> then your driver shouldn't need it.  If you do need it, something is
>> broken, either in your driver or in the twsi driver, and we should
>> figure out what the real problem is.
>> 
>> -- Ian
> 
> Many, many thanks for such a portion of valuable information.
> Went to look for examples in the kernel sources.
> 

Yes!
I found the iiconf.c with iicdev_(readto|writeto) and 
iicbus_transfer_excl definitions.
"Well, now all ducks are ours!"

Thanks once more
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