linux-kernel - Re: [PATCH v2 04/24] PCI: Remove redundant error fabrication when device read fails

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Message-ID: <YXAcws0S2xBvjsDb@robh.at.kernel.org>
Date:   Wed, 20 Oct 2021 08:42:26 -0500
From:   Rob Herring <robh@...nel.org>
To:     Naveen Naidu <naveennaidu479@...il.com>
Cc:     bhelgaas@...gle.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/24] PCI: Remove redundant error fabrication when
 device read fails

On Fri, Oct 15, 2021 at 08:08:45PM +0530, Naveen Naidu wrote:
> An MMIO read from a PCI device that doesn't exist or doesn't respond
> causes a PCI error. There's no real data to return to satisfy the
> CPU read, so most hardware fabricates ~0 data.
> 
> The host controller drivers sets the error response values (~0) and
> returns an error when faulty hardware read occurs. But the error
> response value (~0) is already being set in PCI_OP_READ and
> PCI_USER_READ_CONFIG whenever a read by host controller driver fails.
> 
> Thus, it's no longer necessary for the host controller drivers to
> fabricate any error response.
> 
> This helps unify PCI error response checking and make error check
> consistent and easier to find.
> 
> Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
> ---
>  drivers/pci/access.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)

Reviewed-by: Rob Herring <robh@...nel.org>