linux-kernel - Re: [PATCH] i2c: allow building emev2 without slave mode again

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Date:	Sat, 12 Dec 2015 17:20:57 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	kbuild test robot <lkp@...el.com>, kbuild-all@...org,
	linux-i2c@...r.kernel.org,
	Niklas Söderlund 
	<niklas.soderlund+renesas@...natech.se>, linux-sh@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: allow building emev2 without slave mode again

Hi Arnd,

thanks for looking into this, but I don't get your point yet.

> The slave_cb callback function is supposed to set the 'value'
> here,

Only if a master wants to READ from us.

> but it might return an error not assign the pointer,

An error is only returned if a WRITE from a master was not accepted by
the slave backend.

> It might be best to change the callback to return 'void' and not
> allow it to fail.

We need that because in case of an errno, the slave should send NACK to
the master instead of ACK.

> At least the eeprom slave cannot fail anyway, and it is the only
> implementation we have at the moment.

True. But giving a slave the possibility to NACK a write should be
present IMO.

> Alternatively, the  inline could return an error, and both bus
> drivers check for the error before using 'value'.

Hum, it does return an error?

	return client->slave_cb(client, event, val);

You probably mean something else?

Regards,

   Wolfram


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