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Date:   Thu, 7 Jul 2022 10:38:12 +0100
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Subject: Re: [PATCH v3 03/15] iommu: Always register bus notifiers
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To:     "Tian, Kevin" <kevin.tian@intel.com>,
        Baolu Lu <baolu.lu@linux.intel.com>,
        "joro@8bytes.org" <joro@8bytes.org>
Cc:     "will@kernel.org" <will@kernel.org>,
        "iommu@lists.linux.dev" <iommu@lists.linux.dev>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
        "vasant.hegde@amd.com" <vasant.hegde@amd.com>,
        "mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
        "gerald.schaefer@linux.ibm.com" <gerald.schaefer@linux.ibm.com>,
        "schnelle@linux.ibm.com" <schnelle@linux.ibm.com>,
        "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
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References: <cover.1657034827.git.robin.murphy@arm.com>
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 <BN9PR11MB527610973C947DBA6B2EA8348C839@BN9PR11MB5276.namprd11.prod.outlook.com>
From:   Robin Murphy <robin.murphy@arm.com>
In-Reply-To: <BN9PR11MB527610973C947DBA6B2EA8348C839@BN9PR11MB5276.namprd11.prod.outlook.com>
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On 2022-07-07 07:34, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@linux.intel.com>
>> Sent: Thursday, July 7, 2022 8:21 AM
>>
>> On 2022/7/6 21:43, Robin Murphy wrote:
>>> On 2022-07-06 02:53, Baolu Lu wrote:
>>>> On 2022/7/6 01:08, Robin Murphy wrote:
>>>>>    /*
>>>>>     * Use a function instead of an array here because the domain-type
>>>>> is a
>>>>>     * bit-field, so an array would waste memory.
>>>>> @@ -152,6 +172,10 @@ static int __init iommu_subsys_init(void)
>>>>>                (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
>>>>>                    "(set via kernel command line)" : "");
>>>>> +    /* If the system is so broken that this fails, it will WARN
>>>>> anyway */
>>>>
>>>> Can you please elaborate a bit on this? iommu_bus_init() still return
>>>> errors.
>>>
>>> Indeed, it's commenting on the fact that we don't try to clean up or
>>> propagate an error value further even if it did ever manage to return
>>> one. I feared that if I strip the error handling out of iommu_bus_init()
>>> itself on the same reasoning, we'll just get constant patches from the
>>> static checker brigade trying to add it back, so it seemed like the
>>> neatest compromise to keep that decision where it's obviously in an
>>> early initcall, rather than in the helper function which can be viewed
>>> out of context. However, I'm happy to either expand this comment or go
>>> the whole way and make iommu_bus_init() return void if you think it's
>>> worthwhile.
>>
>> Thanks for the explanation. It would be helpful if the comment could be
>> expanded. In this case, after a long time, people will not consider it
>> an oversight. :-)
>>
> 
> I'd prefer to making iommu_bus_init() return void plus expanding
> the comment otherwise the question arises that if the only caller
> is not interested in the return value then why bother returning it
> in the first place. ????

OK, that's fair enough, will do.

Thanks,
Robin.