linux-kernel - RE: [PATCH v2] staging: kpc2000: kpc_i2c: remove the macros inb_p and outb

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Message-ID: <SN6PR02MB40169CA0F341B5727B806607EEED0@SN6PR02MB4016.namprd02.prod.outlook.com>
Date:   Tue, 11 Jun 2019 13:57:30 +0000
From:   Matt Sickler <Matt.Sickler@...tronics.com>
To:     Geordan Neukum <gneukum1@...il.com>,
        Hao Xu <haoxu.linuxkernel@...il.com>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] staging: kpc2000: kpc_i2c: remove the macros inb_p and
 outb_p

>-----Original Message-----
>From: devel <driverdev-devel-bounces@...uxdriverproject.org> On Behalf Of
>Geordan Neukum
>
>This inb() call looks like a bug. We perform a 64-bit operation when
>talking to this hardware register everywhere else in this driver. Anyone
>have more insight into the hardware with which this driver interacts
>such that they could shed some light on the subject?

That would be me.  I looked at the VHDL for the hardware.  The registers seem to
be aligned to 8 bytes but only use the LS byte of each.  So it probably doesn't
matter whether the memory transactions are 64-bit or 8-bit.
I know the hardware doesn't support byte-enables either, which is probably why
the registers were padded this way.   Probably also why the inb_p and outb_p
macros were redefined.

>Probably a separate issue, but I did notice it as a result of this patch.
>
>Thanks,
>Geordan