Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5ade37de-2582-9e80-b99f-01aab13d991c@intel.com>
Date:   Wed, 18 Jan 2023 19:21:04 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.0
Subject: Re: [PATCH] bitfield: add FIELD_PREP_CONST()
Content-Language: en-US
To:     Johannes Berg <johannes@sipsolutions.net>
CC:     <linux-wireless@vger.kernel.org>
References: <20230118142652.53f20593504b.Iaeea0aee77a6493d70e573b4aa55c91c00e01e4b@changeid>
 <92209c00-7fcf-1592-e97c-f49e7734fdfc@intel.com>
 <3fe52061d5d9e3701f598add5c64f8b3583c31df.camel@sipsolutions.net>
 <b2c78f45-345b-e3ec-20b1-9d18ee0c9f98@intel.com>
 <8b955e4d859aafdf42f1a11f37ddf2a5e47c2610.camel@sipsolutions.net>
From:   Alexander Lobakin <alexandr.lobakin@intel.com>
In-Reply-To: <8b955e4d859aafdf42f1a11f37ddf2a5e47c2610.camel@sipsolutions.net>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bWNKZERsemdZSmlwRlA3R3pvOG9PRVlMOEM4QmNuV0Q0dmk4d01xZXhJRE10?=
 =?utf-8?B?R3BGT1NMclI2M3BLNUFLZUZNYVVUTHA1UXJSTnBKc3dpdkFXNFJGeDBZcHhh?=
 =?utf-8?B?TlJLZWV6QnpUY1A5Q3VqOFhZUldtQUNTaUh4TTByT3U1eE9WKzg1a3VGd3Mv?=
 =?utf-8?B?V25LOEV1TVRYbFp0MFRJZ2pPSXc2YWlmcW5ldzliOFo5QTZtanJPU1BKVXlH?=
 =?utf-8?B?YVdRVlhESW5GWTE3ZTlJVjJyWEtPUXJUa1BGa2RNZXM1NVBpWEhzaHdab2dC?=
 =?utf-8?B?U1BhRXZEMlZqblY0WmpJaDZrbGtmUlRoNy96bitBN2VmMWNmbEE1TTBsYmF3?=
 =?utf-8?B?MzNhL0V3dUxmanhXL0EzcDdOSG1JajJxY0d6Z3Y4K3N5NGh1bHprSkxDOGg5?=
 =?utf-8?B?bTRJcjdQeHNreG1UKzFVVzZoWVk4cEVIZ0V0SHVsN2EvTm02NUJkT1ZKcFpu?=
 =?utf-8?B?ODRUSmhXLzlYUkgrdm9ldG5lY0hPWFNhSlB0ZkM5eTRrN0p0dlBYNVZhMExw?=
 =?utf-8?B?bHR5SlB4azIvcGg3MTJKTnkyNk1WYW9kaThkSnFUU3hUYzJqczR1NGk2NG1y?=
 =?utf-8?B?akNDTmpFWWFBZ2xKbjFJbmFhcWtxczNpWlNQRkl5WGdMbnBEN01ha05RWFlx?=
 =?utf-8?B?NzlxSyt5Zm02dkNnZTNVS0VOaERWeWoxMGdaeFdDSXVGKzBnRmVUVUZwZHZo?=
 =?utf-8?B?VmMvam41eWVPaEhwQS9sZW5vcFA0cUFkVG9PRkpoRVlFSlB2QkhkeEZ6L2xR?=
 =?utf-8?B?TDEydGt5MVRFU3lqM1Vydm8ybloweEN1dmhrekMzd2hGYWdmdCswTTRWZk1P?=
 =?utf-8?B?ay9QUXI5T2ZXeHU4SlZFMFJCMHplLytOU2xiUElNZ3FpWmxwSW5xNmdIMjkr?=
 =?utf-8?B?ZG1DMHVSUWdHR0JYYmZGUTUzbWVidVBFOHBaamZaVGc2TnVkQjZSZDRZbG9Q?=
 =?utf-8?B?TUFBdm5lWVBuWnNQM3RtUHVacDJLSlBCaE5Ubm15bkQ0WFRDRXN3L3JtVGFj?=
 =?utf-8?B?MGR2b3pORGkrZlYxYjBpcXZyTms0U1R6V0g1Y0RvZTN4c3BwbXd3ME96bk5B?=
 =?utf-8?B?Q0lpUGxNdTAxdlZUUGN1ZnQ5c1NraFk3YllTRk5teUdVWkVxRVJZR05XTjBu?=
 =?utf-8?B?bmhwQ2VyTy9OSElkN0llOTNHQzY3dW5qV1EvK1Z0N3VmNlU0aFl3a3NBOExD?=
 =?utf-8?B?VDhJYVVaYVFSeXNtRGg5eS9ZK0VQa1dsTVJKWFdWTkMwZS9FNXIraStYWWJt?=
 =?utf-8?B?VXRlWUNwL3hDYXZ3b1pDVG1SOElOM2lqd3Y2Nk51Wmk5ZCtlckQ4NFplakg4?=
 =?utf-8?B?eFFWbU9iRkVNNk1TakluaU9lT1MvTGhKYmQyb2UrRDRtWXlQS2x4NmlSWFpx?=
 =?utf-8?B?NGRPM1Z4RE0zc1hHK2ZSUTE2Q3FqSVRZZ1FSczJ5Y2ZJTlM1c3NJbWQxanc2?=
 =?utf-8?B?bHhEUTVndjB1Z3VsTE5mdER0VlRmcGJGeWE5TGg3QXpEeHU1UUdQZUVrWUxw?=
 =?utf-8?B?b0pEV2FwY0hZTFNnRmV4VkNmNGkyMEV5bGdIOGg3MU8yaUFmdTBHcEorenFj?=
 =?utf-8?B?RzQ0cnczRkxUKzYzUkJLS25wdkJFcitWNXB6V2lqN05LbkN2QlN3bFhFOSt1?=
 =?utf-8?B?VmVzWkNTaGNzWlo1N20weWoydFh1dkhPL1FaSjZ5SWxsSjg5NkVyWUphQ3Yx?=
 =?utf-8?B?TlZGY25VK29uSkhvU3FVRzIyY01kYWJBODhNMVBCaElrb2t2RjJLK3dEanJv?=
 =?utf-8?B?RnlyWVdKM25CbUpjNXl2ZTJ3aWJ0NDhpcXYzc0JGdUx6UzI0SjUrT29kbmJ1?=
 =?utf-8?B?M1Vhd2FEYWNoWC9TeTc2VVp2NGFIQTNsYmFoclNQZWtVRFdXektLTERreW5l?=
 =?utf-8?B?K3gvSXFRRUlZMitNR3N0VkxKZjBHdkpSVUFMU0E2T1VUbmJtSkxEamhYRUVG?=
 =?utf-8?B?eXVmcFNLcjVsSUdFQlllVHBBV1ZSaUJSVGhrSGNZaUs0MU4xOHpXRlNWblk3?=
 =?utf-8?B?R1VPYlFQdTFGc0hXb08weE5SSHNEUXpOdmloYjh2THlwL0xpWm9IdFhFRzFr?=
 =?utf-8?B?WWZDVG5LaFRpRzRQSWxGajc0b2xianZmV0U2a0JidnFYMTF4SDdNVzVHcG9v?=
 =?utf-8?B?eUJHaG04RzFSYVUxY0RlV0t3VWRCL044UHluK0hpbFh2azl2dGJkak9lT2xo?=
 =?utf-8?B?dkE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 3b3af7c0-02ca-476d-8634-08daf980c5ae
X-MS-Exchange-CrossTenant-AuthSource: DM6PR11MB3625.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2023 18:21:09.6681
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: DniE9NWLDz97A403iG7wYPeloToSwKzAf4Lirfv5F48JAa9nk/teITojic9e97pvgCNT0o8kA+OUJqcNiBk8ALvm23O06dySrXuOhT/NcSs=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB6523
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-wireless.vger.kernel.org>
X-Mailing-List: linux-wireless@vger.kernel.org

From: Johannes Berg <johannes@sipsolutions.net>
Date: Wed, 18 Jan 2023 19:03:24 +0100

> On Wed, 2023-01-18 at 17:49 +0100, Alexander Lobakin wrote:
>>
>> Aaaah right. Seems like we can't avoid introducing a separate macro for
>> that. I like the idea of your patch anyways!
> 
> :)
> 
>> One note re __BF_CHECK_POW2(): can't we reuse is_power_of_2() anyhow?
>> Foe example, by deriving the code of the latter into a macro and then
>> using it in both?
>>
> 
> Well, not directly - for example is_power_of_2() doesn't accept 0, while
> we want to accept 0 (mask being e.g. "0xfull<<60", we already check for
> mask != 0).
> 
> I thought about __BUILD_BUG_ON_NOT_POWER_OF_2 but it uses BUILD_BUG_ON,
> not BUILD_BUG_ON_ZERO, and BUILD_BUG_ON is nicer in most contexts ...
> 
> So you could pull out the expression "((n) & ((n) - 1)) != 0" from all
> four of these, but it doesn't feel worth it.

Aaaah I see.

__BUILD_BUG_ON_NOT_POWER_OF_2_ZERO() then? :D

(mostly joking and not sure it's worth it, up to you)

> 
> johannes

Thanks,
Olek