linux-kernel - Re: [PATCH 1/1] Add strong pullup emulation to w1-gpio master driver.

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Date:	Tue, 12 Nov 2013 05:03:24 +0400
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Evgeny Boger <eugenyboger@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] Add strong pullup emulation to w1-gpio master driver.

Hi

12.11.2013, 03:32, "Evgeny Boger" <eugenyboger@...il.com>:
>> Why did you drop this check? It has nothing with w1-gpio driver
> This check prevents master from implementing "set_pullup"  provided it does support only "write_bit" method.
> The comment above states that
>>  w1_io.c would need to support calling set_pullup before - * the last write_bit operation of a w1_write_8 which it currently - * doesn't.
> which is kind of strange, since it describes what w1_io.c actually does support.
>
> w1_write_8 (w1_io.c:154, https://github.com/torvalds/linux/blob/master/drivers/w1/w1_io.c#L154):
>>                 for (i = 0; i < 8; ++i) {
>>                         if (i == 7)
>>                                 w1_pre_write(dev);
>>                         w1_touch_bit(dev, (byte >> i) & 0x1);
>>                 }
>
> It seems like w1_write_8() calls w1_pre_write(), which in turn calls set_pullup() just before the last write_bit().
>
> I'm not sure why this check was there in the first place.

Please add author of those lines to clarify things.
This doesn't look obvious to me
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