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From: Guenter Roeck <linux@roeck-us.net>
To: Derek Kiernan <derek.kiernan@xilinx.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Michal Simek <michal.simek@xilinx.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Guenter Roeck <linux@roeck-us.net>,
	Dragan Cvetic <dragan.cvetic@xilinx.com>
Subject: [PATCH] misc: xilinx-sdfec: Drop unnecessary NULL check after container_of
Date: Fri, 21 May 2021 13:04:57 -0700	[thread overview]
Message-ID: <20210521200457.2112041-1-linux@roeck-us.net> (raw)

container_of() only returns NULL if the passed pointer is NULL _and_ if
the embedded element is the first element of the structure. Even if that
is the case, testing against it is misleading and possibly dangerous
because the position of the embedded element may change. In this case,
the check is unnecessary since it is known that file->private_data is
never NULL for an open file, and container_of() will therefore also
never be NULL. Drop the check.

Acked-by: Dragan Cvetic <dragan.cvetic@xilinx.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
change since RFC:
	Dropped check for the result of container_of() result instead of
	checking if file->private_data is NULL.

 drivers/misc/xilinx_sdfec.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c
index 23c8448a9c3b..d6e3c650bd11 100644
--- a/drivers/misc/xilinx_sdfec.c
+++ b/drivers/misc/xilinx_sdfec.c
@@ -1013,9 +1013,6 @@ static __poll_t xsdfec_poll(struct file *file, poll_table *wait)
 
 	xsdfec = container_of(file->private_data, struct xsdfec_dev, miscdev);
 
-	if (!xsdfec)
-		return EPOLLNVAL | EPOLLHUP;
-
 	poll_wait(file, &xsdfec->waitq, wait);
 
 	/* XSDFEC ISR detected an error */
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Guenter Roeck <linux@roeck-us.net>
To: Derek Kiernan <derek.kiernan@xilinx.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Michal Simek <michal.simek@xilinx.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Guenter Roeck <linux@roeck-us.net>,
	Dragan Cvetic <dragan.cvetic@xilinx.com>
Subject: [PATCH] misc: xilinx-sdfec: Drop unnecessary NULL check after container_of
Date: Fri, 21 May 2021 13:04:57 -0700	[thread overview]
Message-ID: <20210521200457.2112041-1-linux@roeck-us.net> (raw)

container_of() only returns NULL if the passed pointer is NULL _and_ if
the embedded element is the first element of the structure. Even if that
is the case, testing against it is misleading and possibly dangerous
because the position of the embedded element may change. In this case,
the check is unnecessary since it is known that file->private_data is
never NULL for an open file, and container_of() will therefore also
never be NULL. Drop the check.

Acked-by: Dragan Cvetic <dragan.cvetic@xilinx.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
change since RFC:
	Dropped check for the result of container_of() result instead of
	checking if file->private_data is NULL.

 drivers/misc/xilinx_sdfec.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c
index 23c8448a9c3b..d6e3c650bd11 100644
--- a/drivers/misc/xilinx_sdfec.c
+++ b/drivers/misc/xilinx_sdfec.c
@@ -1013,9 +1013,6 @@ static __poll_t xsdfec_poll(struct file *file, poll_table *wait)
 
 	xsdfec = container_of(file->private_data, struct xsdfec_dev, miscdev);
 
-	if (!xsdfec)
-		return EPOLLNVAL | EPOLLHUP;
-
 	poll_wait(file, &xsdfec->waitq, wait);
 
 	/* XSDFEC ISR detected an error */
-- 
2.25.1


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             reply	other threads:[~2021-05-21 20:05 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-21 20:04 Guenter Roeck [this message]
2021-05-21 20:04 ` [PATCH] misc: xilinx-sdfec: Drop unnecessary NULL check after container_of Guenter Roeck

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