Linux Wireless

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===== About this guide =====

This guide is designed to give you an idea of how to write //linux-wireless// patches. 


===== Subscribe to this page =====

We would like to ask Linux-wireless developers to subscribe to this page on the wiki. Any new policies and best practices on patching to linux-wireless will be posted here. 


===== Prior to sending patches =====

Please **DO NOT** PGP sign patches sent to //linux-wireless//. The reason is that signing patches will encapsulate them into MIME and thereby mangle the patch. Also, please note that we prefer patches inline rather than attachments. 


===== Who to address =====

Send mac80211, cfg80211 and mac80211_hwsim patches as follows: 

<code>To: Johannes Berg <johannes@sipsolutions.net>
CC: linux-wireless@vger.kernel.org, Other Developers</code>

For wireless-drivers patches (except mac80211_hwsim) send patches as:

<code>To: linux-wireless@vger.kernel.org
Cc: Driver maintainers, Other Developers</code>

Where [[en/developers/maintainers|Maintainers]] contains the list of maintainers and mailing lists for the piece of code you are patching. //Other Developers// in this case can be a list of developers (or mailing lists) who you think may like to review this patch or who changed the code you are working on recently. 

Do note that drivers might have special requirements, the best is to check them from the corresponding wiki page. Here's a list for few of them:

  * [[en/users/drivers/ath10k/submittingpatches|ath10k]]
===== Checking state of patches from patchwork =====

All wireless patches are tracked in [[https://patchwork.kernel.org/project/linux-wireless/list/|linux-wireless patchwork project]]. From patchwork you can check the state of the patch and to whom it is assigned. Here's a quick link to see all the patches, no matter what's the state:

[[https://patchwork.kernel.org/project/linux-wireless/list/?state=*]]

Always avoid contacting maintainers directly, they get way too much email already. Instead use the link above to find your patch and see the status. Only in last resort contact the maintainers, and do that by replying to your own patch and ask for status. Do not top post!

Different patchwork states and their meanings:

  * **New**: No action haven't taken yet, expect maybe assigned to a correct maintainer.
  * **Under Review**: The maintainer is waiting review comments from others.
  * **Accepted**: The maintainer has applied the patch to his/her tree.
  * **Rejected**: The maintainer rejected the patch, reasons stated in an email.
  * **Changes Requested**: Either the maintainer or a reviewer requested changes in the patch. The maintainer expects the patch author to submit a new version.
  * **Deferred**: The maintainer has postponed the review of the patch for some reason, for example due to lack of time, patch being to controversial or something else. Patch author doesn't need to take any action, the maintainer will revisit the patch in a later time.
  * **Awaiting Upstream**: The patch depends on an another patch from a different tree, for example a wireless driver needing a specific mac80211 patch to implement a new feature.
  * **RFC**: The patch is sent as Request For Comments. The maintainer expects the patch author to submit a new version.
  * **Superseded**: There's a new version of the patch available, the maintainer has skipped this version.
  * **Not Applicable**: The patch is either not part of wireless subsystem or it will be applied via different trees (for example net-next or driver maintainer trees). The patch is considered as dropped from now on and needs to be resubmitted for the maintainer to reconsider it.

===== Subject =====

If what you are sending is a patch you can use a subject as follows: 


<code>[PATCH] subsystem: fix foo and optimize bar</code>

In case of wireless patches the subsystem can for example be ''mac80211'', ''cfg80211'' or the name of the driver, for example ''ath9k''. There's an easy way to check with git what prefix you should use:

<code>
$ $ git log --oneline --no-merges -10 drivers/net/wireless/ath/ath9k/ar9003_mac.c
8b537686a116 ath9k: add TPC capability to TX descriptor path
315dd1149b60 ath9k: fix getting tx duration for dynack
36678b2b67d7 ath9k: add duration field to ath_tx_status
3ae351abf15f ath9k: set up tx power into the MRR
6a4d05dc0c01 ath9k: move ath9k_debug_sync_cause out of ath9k_hw
e45e91d8812c ath9k: add support for reporting per-chain signal strength
009af8fb69c9 ath9k: Identify first subframe in an A-MPDU
ab2761033576 ath9k: remove useless flag conversation.
ff9bd2d8d95a ath9k_hw: Handle AR_INTR_SYNC_HOST1_(FATAL|PERR) on AR9003
a4a2954ff49e ath9k_hw: Add AR9565 HW support
$
</code>

If your patch is just a proposal you can mark the patch as RFC in the subject: 

<code>[RFC] subsystem: a new way to do foo</code>

If you need to make changes to the patch add a version number inside the brackets:

<code>[PATCH v2] subsystem: fix foo and optimize bar
[PATCH v3] subsystem: fix foo and optimize bar
[PATCH v4] subsystem: fix foo and optimize bar</code>

**Always** increase the version number, no matter how small the change is. The maintainers focus on the latest version and ignore the older versions. Make sure that the maintainers don't need to guess what version he should take, that just creates problems.

Then sending a new version of the patch **always** add a change log, either after the ''%%---%%'' line (three dashes) or in the cover letter.

If a patch in a bigger patchset changes resubmit the whole patchset, even the patches which have not changes. The maintainers look at patchsets as a complete unit, usually they do not want to take patches individually from a patchset.

===== Tree labels =====

Labeling patches with what tree the patch should go to helps maintainers to prioritise and sort patches and avoids unnecessary emails, which saves everyone time and speeds up patch review. Here are some tips how to label wireless patches.

If you want to target your patch to a specific release (for example that the patch should go -rc release not -next) you can inform the maintainer by adding the release number inside the PATCH brackets:
 
<code>[PATCH 4.20] subsystem: fix foo</code>

If you want to make it clear to the maintainer that the patch should NOT go to -rc release but to -next instead you can add "-next" to PATCH brackets:

<code>[PATCH -next] subsystem: fix foo</code>

Alternatively you can specify the exact tree you are targetting by adding the name of the git tree inside PATCH brackets:

<code>[PATCH mac80211] mac80211: fix foo
[PATCH mac80211-next] mac80211: implement very-cool-feature
[PATCH wireless-drivers] ath10k: fix foo
[PATCH wireless-drivers-next] ath10k: implement awesome-feature
</code>


===== Sending large patches or multiple patches =====

You should only send a large patch if your patch does one specific task, or a few of them if they are easy to review. If your work consists of multiple tasks you must split your tasks into separate patches. Each patch must address a small set of tasks to help the maintainers with revision. The rule of thumb here is if you read your patch and if its not clear what the patch is doing then better break it down into separate patches. Patches should also be run through scripts/checkpatch.pl. 

If you are sending multiple patches which depend on each other you can use this format for the subjects: 


<code>[PATCH 0/4] driver_name: introduce foo and bar
[PATCH 1/4] driver_name: introduce get_foo_bars()
[PATCH 2/4] driver_name: fix locking on bar_by_foo()
[PATCH 3/4] driver_name: use foo when barring
[PATCH 4/4] driver_name: optimize bar at init time</code>
On the e-mail with subject, "[PATCH 0/4] driver_name: introduce foo and bar", you would give a brief overview of all the changes. No patch should be included in that e-mail, and as that e-mail will not end up in the change logs it should not contain anything that should be archived, only a rough overview over the purpose of the patch set, no in-depth description which should be in the changelog for each patch. 


===== Format of patches =====

We prefer patches to be inline-text at the end of the body of the e-mail. It's strongly recommended to use git-format-patch and git-send-email tools to submit patches as they use the correct format automatically. Additionally note that we prefer to apply patches with git-am (using the -p1 diff format). A header as follows is then acceptable: 


<code>diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 9b4b4a2..4832e6a 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h</code>

===== Patch tags =====

In order to track who worked on a patch and released the source code under the appropriate licenses used, patch tags are used to track of provenance of patches. This also helps developers review who was in the line of a patch work, who submitted it, and who reviewed it. This information is available from the //git-log//. We currently use, //Signed-off-by//, //Acked-by//, //Cc//, //Reviewed-by// and //Tested-by//. 

Please note that since you are submitting patches inline, after the //Signed-off-by:// lines, you **must** put ''%%---%%'', that is three dashes. Example: 


<code>...
Signed-off-by: Luis R. Rodriguez <mcgrof@example.com>
---
 include/net/ieee80211_regdomains.h |  196 ++++++++
...</code>
Please also read the [[https://www.kernel.org/doc/html/latest/process/submitting-patches.html|official Linux SubmittingPatches]] documentation, especially the **[[https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin|Developer's Certificate of Origin]]**. Do not submit patches unless you have read, understood and agreed to the certificate. 


===== Examples of a patches =====

Below are a few examples of a patches. Only the header is provided for long patches. 
  * Single patch 
<code>From: Michael Buesch
To: John Linville
Cc: linux-wireless, Bcm43xx-dev, Larry Finger
Subject: [PATCH] b43: Remove the "radio hw enabled" message on startup.

This message is useless. Only report state changes.

Signed-off-by: Michael Buesch <mb@example.com>
Cc: Larry Finger <larry.finger@example.com>

---

Index: wireless-dev/drivers/net/wireless/b43/main.c
===================================================================
--- wireless-dev.orig/drivers/net/wireless/b43/main.c   2007-09-20 19:39:06.000000000 +0200
+++ wireless-dev/drivers/net/wireless/b43/main.c        2007-09-20 20:06:24.000000000 +0200
@@ -2227,9 +2227,6 @@ static int b43_chip_init(struct b43_wlde
       if (err)
               goto err_gpio_cleanup;
       b43_radio_turn_on(dev);
-       dev->radio_hw_enable = b43_is_hw_radio_enabled(dev);
-       b43dbg(dev->wl, "Radio %s by hardware\n",
-              dev->radio_hw_enable ? "enabled" : "disabled");

       b43_write16(dev, 0x03E6, 0x0000);
       err = b43_phy_init(dev);
@@ -3251,6 +3248,9 @@ static void setup_struct_wldev_for_init(
 {
       /* Flags */
       dev->reg124_set_0x4 = 0;
+       /* Assume the radio is enabled. If it's not enabled, the state will
+        * immediately get fixed on the first periodic work run. */
+       dev->radio_hw_enable = 1;

       /* Stats */
       memset(&dev->stats, 0, sizeof(dev->stats));
-</code>
    * Multiple patches 
<code>From: Luis R. Rodriguez
To: John Linville
Cc: linux-wireless, Michael Wu, Johannes Berg, Daniel Drake, Larry Finger
Subject: [PATCH 3/5] Wireless: add IEEE-802.11 regualtory domain module

This adds the regulatory domain module. It provides a way to
allocate and construct a regulatory domain based on the current
map. This module provides no enforcement, it just does the actual
building of the regdomain and returns it as defined in ieee80211_regdomains.h

This module depends on the ISO3166-1 module.

Signed-off-by: Luis R. Rodriguez <mcgrof@example.com>

---
 include/net/ieee80211_regdomains.h |  196 ++++++++
 net/wireless/Kconfig               |   16 +
 net/wireless/Makefile              |    1 +
 net/wireless/reg_common.h          |  138 ++++++
 net/wireless/regdomains.c          |  751 ++++++++++++++++++++++++++++++
 net/wireless/regulatory_map.h      |  887 ++++++++++++++++++++++++++++++++++++
 6 files changed, 1989 insertions(+), 0 deletions(-)
 create mode 100644 include/net/ieee80211_regdomains.h
 create mode 100644 net/wireless/reg_common.h
 create mode 100644 net/wireless/regdomains.c
 create mode 100644 net/wireless/regulatory_map.h

diff --git a/include/net/ieee80211_regdomains.h b/include/net/ieee80211_regdomains.h
new file mode 100644
index 0000000..adf4de4
--- /dev/null
+++ b/include/net/ieee80211_regdomains.h
@@ -0,0 +1,196 @@
+#ifndef _IEEE80211_REGDOMAIN_H
+#define _IEEE80211_REGDOMAIN_H
+/*
... ETC ...</code>

===== Frequent problems in patch submissions =====

==== Patch version missing ====

If you send a new version of the patch or patchset you should always add a version number. The first version does not need to be shown but starting from second version the version number must be available:

  [PATCH] ath10k: fix DMA allocation
  [PATCH v2] ath10k: fix DMA allocation
  [PATCH v3] ath10k: fix DMA allocation
  ...
  [PATCH v11] ath10k: fix DMA allocation

You can add the version with switch ''--subject-prefix'':
  
  git format-patch --subject-prefix="PATCH v2"

==== Changelog missing ====

When sending a new version of a patch or patchset you should **always** add a changelog so that maintainer can easily see what has changed.

If you have just one patch you can add the changelog after the ''%%---%%'' (three dashes) line.

If you have multiples patches (called a patchset) add the changelog to the cover letter. You can create the cover letter with the switch ''--cover-letter'':

  git format-patch --subject-prefix="PATCH v2" --cover-letter
  
==== Signed-off-by missing ====

Read [[https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin|Developer's Certificate of Origin]] and add Signed-off-by to the commit log.

==== Format issues ====

Patch is somehow whitespace damaged, for example tabs converted to spaces, extra new lines or other modifications which prevent applying the patch without manual fixing. Or the mail is in HTML format which most of the mailing lists even block silently.

The best way to avoid all formatting issues is to use [[https://www.kernel.org/pub/software/scm/git/docs/git-send-email.html|git send-email]]. See [[en/developers/Documentation/git-guide|linux-wireless git guide]] for more information.

==== Fixes line is incorrect ====

The correct format for the commit references in Fixes line is the 12 initial digits
of the SHA1_ID of the commit, followed by a space, followed by the
commit log message header line text enclosed in parentheses and
double quotes with no line breaks whatsoever.

Example:

  Fixes: c742e623e941 ("mwifiex: sdio card reset enhancement")

==== Commit reference is wrong ====

The correct format for the commit references in commit logs is to start with the string "commit", followed by a space, followed 12 initial digits
of the SHA1_ID of the commit, followed by a space and followed by the
commit log message header line text enclosed in parentheses.

Example:

<code>
commit f99a6abe59e096cc2c753e667c19f22022e3bef4
Author: Sara Sharon <sara.sharon@intel.com>
Date:   Sun Mar 5 18:35:02 2017 +0200

    iwlwifi: mvm: memset binding before setting values
    
    The changes in commit 9415af7f306b ("iwlwifi: mvm: support new binding
    API") assigned values that were later memset to 0.  Move the memset
    earlier.
    
    Fixes: 9415af7f306b ("iwlwifi: mvm: support new binding API")
    Signed-off-by: Sara Sharon <sara.sharon@intel.com>
    Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
</code>

==== Commit title is wrong ====

The correc tformat for the commit title is name of driver, followed by a colon, followed by a space and then followed by the actual title. You can use ''git log'' to check older commits and see what prefix was used:

<code>
$ git log --oneline --follow --no-merges -20 drivers/net/wireless/marvell/mwifiex/11ac.c
277b024e5e3d mwifiex: move under marvell vendor directory
65da33f5557f mwifiex: update Copyright to 2014
cf831ffe4473 mwifiex: fix IE parsing issues
d51246481c7f mwifiex: save and copy AP's VHT capability info correctly
5f6d5983394f mwifiex: add VHT support for TDLS
9ed230bcbab7 mwifiex: pass ieee80211_vht_cap to mwifiex_fill_vht_cap_tlv
406d702b47a2 mwifiex: improve readability in 11ac mcsmap to maxrate conversion
89467d8ca21b mwifiex: make 11ac mcs rate tables global and const
7abf4129e6df mwifiex: make use of IEEE80211_VHT_MCS_NOT_SUPPORTED
0648f3a4b0e9 mwifiex: correct bss_mode check while appending vht operation IE
2b6254dacfe6 mwifiex: use separate AMPDU tx/rx window sizes in 11ac networks
83c78da983d6 mwifiex: add support to configure VHT for AP mode
a5f390562a37 mwifiex: add 802.11AC support
</code>

==== Too many patches ====

The recommend size is 10-12 patches per patchset. More than that it gets difficult for reviewers and maintainers. Of course there's no hard rule, for simple patches more than that might be ok but then again for more complex patches even 10 patches per patchset might be too much.

==== Resubmit the whole patchset =====

Even if just one patch has changed in a patch series resubmit the whole patchset (and remember to increase the version number), do not just resubmit that one changed patch. The reason is that it's difficult to apply patches in correct order when some of them are submitted separately.

==== Commit log does not answer "Why?" ====

The commit log should //always// answer the question "Why?" and describe the reason what
motivated to implement the patch. This is the most important part of the commit log as this helps maintainers, backports, distros etc to make decisions if the patch is important for them or not and to what release it should go.

The commit log needs to tell why you wrote the patch. If you fixed a bug give a short summary of the bug (can be a long one as well, of course) from user's point of view, and if there's a publically available bug report include a link to that. If you are fixing a warning from a compiler or a static checker add the warning from tool. Or if it's just code cleanup or fixing a theoretical issue, and does not have practical user visible changes, mention that also.

==== Do not top post and edit your quotes ====

Top posting makes following email threads hard to follow and also it makes use of patchwork more difficult, which gets the maintainers grumpy as you are making their work more difficult. So do not top post and instead edit your quotes properly.

<code>A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

A: No.
Q: Should I include quotations after my reply?
</code>

More info: http://www.idallen.com/topposting.html

==== Use RFC or RFT for patches not ready ====

If the patches are not yet ready to be applied by the maintainer, mark them as RFC (Request For Comments) or RFT (Request For Test). This way the maintainer can easily see that the patch should not be applied yet. This saves a lot of maintainer's time.


===== More references =====

Here is a list of links to help you write better patches 

  * [[https://www.kernel.org/doc/html/latest/process/submitting-patches.html|SubmittingPatches]]
  * https://kernelnewbies.org/FirstKernelPatch
  * [[http://linux.yyz.us/patch-format.html|http://linux.yyz.us/patch-format.html]] 
  * [[https://www.ozlabs.org/~akpm/stuff/tpp.txt|Andrew Morton's ''The perfect patch'']] 
  * [[http://lkml.kernel.org/r/20171026223701.GA25649@bhelgaas-glaptop.roam.corp.google.com|Make Bjorn's life easier (and grease the path of your patch)]]
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