urtwn(4): add error handling for urtwn_write_X() functions

[avos]

Summary

• Return an error when urtwn_write_<smth>() fails.
• Handle errors from them in:
• urtwn_fw_cmd();
• urtwn_llt_write();
• urtwn_efuse_*();
• urtwn_*_power_on();
• urtwn_*_dma_init();
• urtwn_mac_init();
• urtwn_init();
• Call ieee80211_stop() when urtwn_init() fails.

Test Plan

Tested with RTL8188EU, STA mode

[avos]

Fix locking

[kevlo]

The error handing is bogus. Is it really needded?

[avos]

In D4291#90697, @kevlo wrote:

The error handing is bogus. Is it really needded?

As for me, it works fine without this code. But:

• ieee80211_stop() will mark this interface as stopped when an error in urtwn_init() happens (for example, some time ago I have seen 'timeout waiting for checksum report' error). As a result, after an error - with this change - you can try to reinit the device with 'ifconfig wlan0 up'
• error handling for <name>_write() / <name>_read is already implemented for other usb wlan drivers; I have not seen any reason to drop it here.

[kevlo]

In D4291#90993, @s3erios_gmail.com wrote:

In D4291#90697, @kevlo wrote:

The error handing is bogus. Is it really needded?

As for me, it works fine without this code. But:

• ieee80211_stop() will mark this interface as stopped when an error in urtwn_init() happens (for example, some time ago I have seen 'timeout waiting for checksum report' error). As a result, after an error - with this change - you can try to reinit the device with 'ifconfig wlan0 up'

I had seen this message once, but it appears I didn't fix it :(

• error handling for <name>_write() / <name>_read is already implemented for other usb wlan drivers; I have not seen any reason to drop it here.

Well, I'm not against making changes, I just think why we introduced
unaffected code just because others are also doing it.

[avos]

In D4291#91096, @kevlo wrote:

In D4291#90993, @s3erios_gmail.com wrote:

In D4291#90697, @kevlo wrote:

The error handing is bogus. Is it really needded?

As for me, it works fine without this code. But:

• ieee80211_stop() will mark this interface as stopped when an error in urtwn_init() happens (for example, some time ago I have seen 'timeout waiting for checksum report' error). As a result, after an error - with this change - you can try to reinit the device with 'ifconfig wlan0 up'

I had seen this message once, but it appears I didn't fix it :(

This is not the only case - for example, user may forget to install the corresponding firmware.

• error handling for <name>_write() / <name>_read is already implemented for other usb wlan drivers; I have not seen any reason to drop it here.

Well, I'm not against making changes, I just think why we introduced
unaffected code just because others are also doing it.

It may help when device <-> USB connection is not stable (so, the driver will not hang when device disconnects + there is a guarantee, that the device will be configured properly).