linux-kernel - Re: [PATCH v3 02/25] PCI: Set error response in config access defines when ops->read() fails

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Date:   Thu, 21 Oct 2021 17:59:18 +0200
From:   Pali Rohár <pali@...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,
        linux-arm-kernel@...ts.infradead.org, linux-hyperv@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-renesas-soc@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, Rob Herring <robh@...nel.org>,
        skhan@...uxfoundation.org, Robert Richter <rric@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM IPROC ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Jianjun Wang <jianjun.wang@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Shawn Guo <shawn.guo@...aro.org>,
        Xiaowei Song <songxiaowei@...ilicon.com>,
        Binghui Wang <wangbinghui@...ilicon.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Joyce Ooi <joyce.ooi@...el.com>,
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        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Nirmal Patel <nirmal.patel@...ux.intel.com>,
        Jonathan Derrick <jonathan.derrick@...ux.dev>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
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        Marc Zyngier <maz@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
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        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Toan Le <toan@...amperecomputing.com>
Subject: Re: [PATCH v3 02/25] PCI: Set error response in config access
 defines when ops->read() fails

On Thursday 21 October 2021 20:37:27 Naveen Naidu wrote:
> Make PCI_OP_READ and PCI_USER_READ_CONFIG set the data value with error
> response (~0), when the PCI device read by a host controller fails.
> 
> This ensures that the controller drivers no longer need to fabricate
> (~0) value when they detect error. It also  gurantees that the error
> response (~0) is always set when the controller drivers fails to read a
> config register from a device.
> 
> This makes error response fabrication consistent and helps in removal of
> a lot of repeated code.
> 
> Suggested-by: Rob Herring <robh@...nel.org>
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>

Reviewed-by: Pali Rohár <pali@...nel.org>

> ---
>  drivers/pci/access.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index 46935695cfb9..0f732ba2f71a 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -42,7 +42,10 @@ int noinline pci_bus_read_config_##size \
>  	if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;	\
>  	pci_lock_config(flags);						\
>  	res = bus->ops->read(bus, devfn, pos, len, &data);		\
> -	*value = (type)data;						\
> +	if (res)							\
> +		SET_PCI_ERROR_RESPONSE(value);				\
> +	else								\
> +		*value = (type)data;					\
>  	pci_unlock_config(flags);					\
>  	return res;							\
>  }
> @@ -228,7 +231,10 @@ int pci_user_read_config_##size						\
>  	ret = dev->bus->ops->read(dev->bus, dev->devfn,			\
>  					pos, sizeof(type), &data);	\
>  	raw_spin_unlock_irq(&pci_lock);				\
> -	*val = (type)data;						\
> +	if (ret)							\
> +		SET_PCI_ERROR_RESPONSE(val);				\
> +	else								\
> +		*val = (type)data;					\
>  	return pcibios_err_to_errno(ret);				\
>  }									\
>  EXPORT_SYMBOL_GPL(pci_user_read_config_##size);
> -- 
> 2.25.1
>