linux-kernel - RE: [PATCH v3 6/6] iommu: Propagate ret for a potential soft failure EINVAL

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Message-ID: <BN9PR11MB5276A69368B6E06E2C86EA058C4C9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 20 Sep 2022 06:50:22 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        "yong.wu@...iatek.com" <yong.wu@...iatek.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>
CC:     "jgg@...dia.com" <jgg@...dia.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: RE: [PATCH v3 6/6] iommu: Propagate ret for a potential soft failure
 EINVAL

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Thursday, September 15, 2022 3:59 PM
> 
> Following the new rules in include/linux/iommu.h kdocs, EINVAL now can be
> used to indicate that domain and device are incompatible by a caller that
> treats it as a soft failure and tries attaching to another domain.
> 
> Either mtk_iommu or virtio driver has a place that returns a hard failure
> instead of the return value from the function call, where an incompatible
> errno EINVAL could potentially occur.

in both cases there is no EINVAL returned from the calling stack

IMHO error propagation is the right way even w/o talking about EINVAL
otherwise we may miss ENOMEM etc.

> 
> Propagate the real return value to not miss a potential soft failure.
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>

Apart from that comment,

Reviewed-by: Kevin Tian <kevin.tian@...el.com>