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2018-02-21T02:49:47Z

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Psmay: /* Setting permissions for an arbitrary device */

2018-02-21T02:47:15Z

Setting permissions for an arbitrary device

Psmay: Created page with "==Setting permissions for an arbitrary device== This is the basic info on how I got an ST-Link 2 clone to be accessible to users in a specific group. The platform is Linux Mi..."

2017-12-04T15:54:47Z

Created page with "==Setting permissions for an arbitrary device== This is the basic info on how I got an ST-Link 2 clone to be accessible to users in a specific group. The platform is Linux Mi..."

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==Setting permissions for an arbitrary device==

This is the basic info on how I got an ST-Link 2 clone to be accessible to users in a specific group. The platform is Linux Mint 17.3 on x64.

===General rule===

The general form of the rule is

<nowiki>
SUBSYSTEM=="usb", ACTION=="add", ATTRS{idVendor}=="<vendor ID hex>", ATTRS{idProduct}=="<product ID hex>", MODE:="<4-digit octal permissions>", GROUP:="<owning group name>"</nowiki>

Take careful note of the equals symbols used; the matching parts of the rule use a double-equal operator <code>==</code> while the assignments use a colon-equal operator <code>:=</code>. (Some others' examples also have a single-equal operator <code>=</code> for assignments, but that notation didn't work in my environment.)

This rule is to be placed in a file <code><nowiki>/etc/udev/rules.d/<two-digit priority number>-<description>.rules</nowiki></code>. The two-digit priority number is present for the express purpose of placing the filename at a given point in alphabetical sorting order.

For more information about what this actually does, see documentation for udev rules.

===Example===

Use lsusb to determine the vendor id and product id. For this example, the output contained the line:

<nowiki>
$ lsusb
...
Bus 006 Device 020: ID 0483:3748 STMicroelectronics ST-LINK/V2
...</nowiki>

Here, the device ID is two 16-bit hex values separated by a colon: <code>0483:3748</code>. The left and right parts are the vendor ID and the product ID, respectively.

I've decided that the group which owns the device is called <code>usbusers</code>, and to this end I have created the group, added myself to the group, then logged out and back in for the change to be effective.

I've decided I want to limit access to the owner (root) and group, so I've chosen the permissions <code>0660</code>. To allow access to all users, set the mode to <code>0666</code> and don't bother with the <code>GROUP</code> clause.

The rules file will be named <code>45-psm-stlink.rules</code>, having the arbitrarily chosen priority of 45.

<code>/etc/udev/rules.d/45-psm-stlink.rules</code>:

<nowiki>
SUBSYSTEM=="usb", ACTION=="add", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="3748", MODE:="0660", GROUP:="usbusers"</nowiki>

Once the rules file is in place, restart the udev service.

====Check the work====

Detach (if attached) then reattach the device. Run lsusb once again to see the updated bus and device number:

<nowiki>
$ lsusb
...
Bus 006 Device 021: ID 0483:3748 STMicroelectronics ST-LINK/V2
...
</nowiki>

To examine whether the permissions change took, do

<nowiki>
ls -l /dev/bus/usb/<bus number>/<device number></nowiki>

For the bus 006 and device 021:

<nowiki>
$ ls -l /dev/bus/usb/006/021
crw-rw---- 1 root usbusers 189, 660 Dec 4 10:46 /dev/bus/usb/006/021</nowiki>

Note that the group is <code>usbusers</code> and that only the user and group have access; our rule has worked.

← Older revision		Revision as of 02:49, 21 February 2018
Line 65:		Line 65:

	Note that the group is <code>usbusers</code> and that only the user and group have access; our rule has worked.		Note that the group is <code>usbusers</code> and that only the user and group have access; our rule has worked.
		+
		+	==udev rules for Maple Mini development==
		+
		+	As specified in [https://github.com/rogerclarkmelbourne/Arduino_STM32/wiki/Using-a-generic-stm32-board-on-linux-with-Maple-bootloader the stm32duino doc]:
		+
		+	/etc/udev/rules.d/45-maple.rules:
		+
		+	<nowiki>
		+	ATTRS{idProduct}=="1001", ATTRS{idVendor}=="0110", MODE="664", GROUP="plugdev"
		+	ATTRS{idProduct}=="1002", ATTRS{idVendor}=="0110", MODE="664", GROUP="plugdev"
		+	ATTRS{idProduct}=="0003", ATTRS{idVendor}=="1eaf", MODE="664", GROUP="plugdev" SYMLINK+="maple"
		+	ATTRS{idProduct}=="0004", ATTRS{idVendor}=="1eaf", MODE="664", GROUP="plugdev" SYMLINK+="maple"</nowiki>

	==...==		==...==

← Older revision		Revision as of 02:47, 21 February 2018
Line 65:		Line 65:

	Note that the group is <code>usbusers</code> and that only the user and group have access; our rule has worked.		Note that the group is <code>usbusers</code> and that only the user and group have access; our rule has worked.
		+
		+	==...==

Udev - Revision history

Psmay: /* ... */

Psmay: /* Setting permissions for an arbitrary device */

Psmay: Created page with "==Setting permissions for an arbitrary device== This is the basic info on how I got an ST-Link 2 clone to be accessible to users in a specific group. The platform is Linux Mi..."