[PATCH][next] block: scsi_ioctl: Avoid the use of one-element arrays

["Gustavo A. R. Silva" <gustavoars@kernel.org>]

One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type compat_caddr_t: 'compat_caddr_t unused'[2],
once it seems this field is actually never used.

Also, update struct cdrom_generic_command in UAPI by adding an
anonimous union to avoid using the one-element array _reserved_.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] https://github.com/KSPP/linux/issues/86

Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/5f76f5d0.qJ4t%2FHWuRzSW7bTa%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 block/scsi_ioctl.c         | 6 +++---
 include/uapi/linux/cdrom.h | 5 ++++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 600e38cb69b2..2dfb699389df 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -643,7 +643,7 @@ struct compat_cdrom_generic_command {
 	unsigned char	data_direction;
 	compat_int_t	quiet;
 	compat_int_t	timeout;
-	compat_caddr_t	reserved[1];
+	compat_caddr_t	unused;
 };
 #endif
 
@@ -665,7 +665,7 @@ static int scsi_get_cdrom_generic_arg(struct cdrom_generic_command *cgc,
 			.data_direction	= cgc32.data_direction,
 			.quiet		= cgc32.quiet,
 			.timeout	= cgc32.timeout,
-			.reserved[0]	= compat_ptr(cgc32.reserved[0]),
+			.unused		= compat_ptr(cgc32.unused),
 		};
 		memcpy(&cgc->cmd, &cgc32.cmd, CDROM_PACKET_SIZE);
 		return 0;
@@ -690,7 +690,7 @@ static int scsi_put_cdrom_generic_arg(const struct cdrom_generic_command *cgc,
 			.data_direction	= cgc->data_direction,
 			.quiet		= cgc->quiet,
 			.timeout	= cgc->timeout,
-			.reserved[0]	= (uintptr_t)(cgc->reserved[0]),
+			.unused		= (uintptr_t)(cgc->unused),
 		};
 		memcpy(&cgc32.cmd, &cgc->cmd, CDROM_PACKET_SIZE);
 
diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
index 2817230148fd..6c34f6e2f1f7 100644
--- a/include/uapi/linux/cdrom.h
+++ b/include/uapi/linux/cdrom.h
@@ -289,7 +289,10 @@ struct cdrom_generic_command
 	unsigned char		data_direction;
 	int			quiet;
 	int			timeout;
-	void			__user *reserved[1];	/* unused, actually */
+	union {
+		void		__user *reserved[1];	/* unused, actually */
+		void            __user *unused;
+	};
 };
 
 /*
-- 
2.27.0