From: "Zhang, Ning A" <ning.a.zhang@intel.com>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: question about V4L2_MEMORY_USERPTR on 64bit applications
Date: Fri, 12 Oct 2018 03:04:01 +0000 [thread overview]
Message-ID: <1539313441.21249.3.camel@intel.com> (raw)
Hi,
I have question about V4L2_MEMORY_USERPTR on 64bit applications.
struct v4l2_buffer {
__u32 index;
__u32 type;
__u32 bytesused;
__u32 flags;
__u32 field;
struct timeval timestamp;
struct v4l2_timecode timecode;
__u32 sequence;
/* memory location */
__u32 memory;
union {
__u32 offset;
unsigned long userptr; <<<--- this is a 32bit addr.
struct v4l2_plane *planes;
__s32 fd;
} m;
__u32 length;
__u32 reserved2;
__u32 reserved;
};
when use a 64bit application, memory from malloc is 64bit address.
memory from GPU (eg, intel i915) are also 64bit address.
when use these kind of memory as V4L2_MEMORY_USERPTR, address will be
truncated into 32bit.
this would be error, but actually not. I really don't understand.
BR.
Ning.
next reply other threads:[~2018-10-12 10:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-12 3:04 Zhang, Ning A [this message]
2018-10-12 3:25 ` question about V4L2_MEMORY_USERPTR on 64bit applications Bing Bu Cao
2018-10-12 4:33 ` Zhang, Ning A
2018-10-12 5:22 ` tbhardwa
2018-10-14 0:11 ` Eugene Syromiatnikov
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