linux-kernel - Re: [PATCH] scsi/ata: Use unsigned int for cmd's type in ioctls in scsi_host

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Message-ID: <1539977925.81977.55.camel@acm.org>
Date:   Fri, 19 Oct 2018 12:38:45 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Jens Axboe <axboe@...nel.dk>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        "Manoj N. Kumar" <manoj@...ux.vnet.ibm.com>,
        "Matthew R. Ochs" <mrochs@...ux.vnet.ibm.com>,
        Uma Krishnan <ukrishn@...ux.vnet.ibm.com>,
        Bradley Grove <linuxdrivers@...otech.com>,
        Don Brace <don.brace@...rosemi.com>,
        Brian King <brking@...ibm.com>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        esc.storagedev@...rosemi.com
Subject: Re: [PATCH] scsi/ata: Use unsigned int for cmd's type in ioctls in
 scsi_host_template

On Fri, 2018-10-19 at 10:57 -0700, Nathan Chancellor wrote:
> Clang warns several times in the scsi subsystem (trimmed for brevity):
> 
> drivers/scsi/hpsa.c:6209:7: warning: overflow converting case value to
> switch condition type (2147762695 to 18446744071562347015) [-Wswitch]
>         case CCISS_GETBUSTYPES:
>              ^
> drivers/scsi/hpsa.c:6208:7: warning: overflow converting case value to
> switch condition type (2147762694 to 18446744071562347014) [-Wswitch]
>         case CCISS_GETHEARTBEAT:
>              ^
> 
> The root cause is that the _IOC macro can generate really large numbers,
> which don't find into type 'int', which is used for the cmd paremeter in
> the ioctls in scsi_host_template. My research into how GCC and Clang are
> handling this at a low level didn't prove fruitful. However, looking at
> the rest of the kernel tree, all ioctls use an 'unsigned int' for the
> cmd parameter, which will fit all of the _IOC values in the scsi/ata
> subsystems.
> 
> Make that change because none of the ioctls expect to take a negative
> value, it brings the ioctls inline with the reset of the kernel, and it
> removes ambiguity, which is never good when dealing with compilers.

Reviewed-by: Bart Van Assche <bvanassche@....org>