From: John Garry <john.garry@huawei.com>
To: "Ewan D. Milne" <emilne@redhat.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
"Alim Akhtar" <alim.akhtar@samsung.com>,
Avri Altman <avri.altman@wdc.com>,
"Doug Gilbert" <dgilbert@interlog.com>,
<linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <james.smart@broadcom.com>
Subject: Re: [PATCH 1/4] scsi: core: constify pointer to scsi_host_template
Date: Tue, 12 Apr 2022 08:57:39 +0100 [thread overview]
Message-ID: <b6af3fe8-db9a-b5dc-199f-21c05d7664a2@huawei.com> (raw)
In-Reply-To: <c121430b1b5c8f5816b2b42b9178d00889260c90.camel@redhat.com>
On 08/04/2022 20:31, Ewan D. Milne wrote:
> On Fri, 2022-04-08 at 13:57 +0100, John Garry wrote:
>> On 08/04/2022 13:32, Krzysztof Kozlowski wrote:
>>> On 08/04/2022 14:14, John Garry wrote:
>>>> On 08/04/2022 11:30, Krzysztof Kozlowski wrote:
>>>>> Several pointers to 'struct scsi_host_template' do not modify it, so
>>>>> made them const for safety.
>>>>>
>>>> Is this standard practice? What is so special here?
>>> This is standard practice and there is nothing special here. Pointers to
>>> const are preferred because:
>>> 1. They add safety if data is actually const. This is not yet the case,
>>> but scsi_host_template allocation could be made const with some effort.
>
> This seems unlikely, because some drivers, e.g. vmw_pvscsi and scsi_debug,
> modify the scsi_host_template based on things like module parameters.
>
The standard flow is:
shost = scsi_host_alloc(sht, )
// modify shost, like
shost->cmd_per_lun = 5;
scsi_add_host(shost)
Is there some reason for which those two drivers can't follow that?
>>
>> To me this seems better, but I think that some drivers might modify
>> their scsi_host_template (so not possible)
>
> Several drivers modify scsi_host_template, e.g. .can_queue, .cmd_per_lun
>
> There is also code in lpfc_create_port() that initializes a scsi_host_template
> that is embedded in the lpfc_hba struct. I don't think it gets modified after
> scsi_add_host() but it seems like driver maintainers might expect to be able
> to do so, in general.
>
Even so, I don't see why other drivers cannot declare their
scsi_host_template as const. C would have no problem with sht not be
being const for this:
struct Scsi_Host *scsi_host_alloc(const struct scsi_host_template *sht, )
thanks,
John
next prev parent reply other threads:[~2022-04-12 9:30 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 10:30 [PATCH 1/4] scsi: core: constify pointer to scsi_host_template Krzysztof Kozlowski
2022-04-08 10:30 ` [PATCH 2/4] scsi: core: fix white-spaces Krzysztof Kozlowski
2022-05-04 8:47 ` Krzysztof Kozlowski
2022-04-08 10:30 ` [PATCH 3/4] scsi: ufs: ufshcd-pltfrm: constify pointed data Krzysztof Kozlowski
2022-04-08 10:30 ` [PATCH 4/4] scsi: ufs: ufshcd: " Krzysztof Kozlowski
2022-04-08 14:35 ` Bart Van Assche
2022-04-08 12:14 ` [PATCH 1/4] scsi: core: constify pointer to scsi_host_template John Garry
2022-04-08 12:32 ` Krzysztof Kozlowski
2022-04-08 12:57 ` John Garry
2022-04-08 19:31 ` Ewan D. Milne
2022-04-12 7:57 ` John Garry [this message]
2022-04-20 7:03 ` Christoph Hellwig
2022-04-25 8:58 ` John Garry
2022-04-25 9:22 ` Krzysztof Kozlowski
2022-04-25 13:04 ` John Garry
2022-04-26 1:16 ` Bart Van Assche
2022-04-26 1:54 ` Douglas Gilbert
2022-04-26 4:13 ` Bart Van Assche
2022-04-27 1:47 ` Douglas Gilbert
2022-05-06 16:42 ` Krzysztof Kozlowski
2022-05-09 11:28 ` John Garry
2022-05-09 13:20 ` Krzysztof Kozlowski
2022-05-09 14:50 ` John Garry
2022-05-11 8:31 ` Christoph Hellwig
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