StackOverflow2013

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plurals

PO
primarykey
Id
15809221
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
1
CommunityOwnedDate
CreationDate
2013-04-04T10:57:03.017
FavoriteCount
0
LastActivityDate
2014-02-18T17:52:40.707
LastEditDate
2014-02-18T17:52:40.707
LastEditorUserId
198536
OwnerUserId
1381158
ParentId
15807846
PostTypeId
2
Score
66
ViewCount
0
LastEditorDisplayName
text
Body
An <code>ioctl</code>, which means "input-output control" is a kind of device-specific system call. There are only a few system calls in Linux (300-400), which are not enough to express all the unique functions devices may have. So a driver can define an ioctl which allows a userspace application to send it orders. However, ioctls are not very flexible and tend to get a bit cluttered (dozens of "magic numbers" which just work... or not), and can also be insecure, as you pass a buffer into the kernel - bad handling can break things easily. An alternative is the <code>sysfs</code> interface, where you set up a file under <code>/sys/</code> and read/write that to get information from and to the driver. An example of how to set this up: <pre><code>static ssize_t mydrvr_version_show(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "%s\n", DRIVER_RELEASE); } static DEVICE_ATTR(version, S_IRUGO, mydrvr_version_show, NULL); </code></pre> And during driver setup: <pre><code>device_create_file(dev, &dev_attr_version); </code></pre> You would then have a file for your device in <code>/sys/</code>, for example, <code>/sys/block/myblk/version</code> for a block driver. Another method for heavier use is netlink, which is an IPC (inter-process communication) method to talk to your driver over a BSD socket interface. This is used, for example, by the WiFi drivers. You then communicate with it from userspace using the <code>libnl</code> or <code>libnl3</code> libraries.
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1. This table or related slice is empty.
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1. POIOCTL Linux device driver
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1. PTAnswer
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1. USwallyk
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1. USInductiveload
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1. POIOCTL Linux device driver
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