linux-kernel - RE: [PATCH v4] scsi/ata: Use unsigned int for cmd's type in ioctls in scsi_host

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Date:   Mon, 28 Jan 2019 16:16:34 +0000
From:   <Don.Brace@...rochip.com>
To:     <natechancellor@...il.com>, <axboe@...nel.dk>,
        <aacraid@...rosemi.com>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <manoj@...ux.ibm.com>,
        <mrochs@...ux.ibm.com>, <ukrishn@...ux.ibm.com>,
        <linuxdrivers@...otech.com>, <don.brace@...rosemi.com>,
        <brking@...ibm.com>
CC:     <linux-ide@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>, <esc.storagedev@...rosemi.com>,
        <ndesaulniers@...gle.com>, <bvanassche@....org>
Subject: RE: [PATCH v4] scsi/ata: Use unsigned int for cmd's type in ioctls in
 scsi_host_template


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.

Link: https://github.com/ClangBuiltLinux/linux/issues/85
Link: https://github.com/ClangBuiltLinux/linux/issues/154
Link: https://github.com/ClangBuiltLinux/linux/issues/157
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: Bart Van Assche <bvanassche@....org>

 static void __exit esas2r_exit(void)
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c index ff67ef5d5347..28cfd3d01c5a 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -251,10 +251,11 @@ static int number_of_controllers;

Acked-by: Don Brace <don.brace@...rosemi.com>

 
diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c
index f564af8949e8..5d9ccbab7581 100644
--- a/drivers/scsi/smartpqi/smartpqi_init.c
+++ b/drivers/scsi/smartpqi/smartpqi_init.c
@@ -6043,7 +6043,8 @@ static int pqi_passthru_ioctl(struct pqi_ctrl_info *ctrl_info, void __user *arg)
 	return rc;
 }

Acked-by: Don Brace <don.brace@...rosemi.com>