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Tue, 12 Jul 2022 13:51:11 +0000 Received: from DS0PR11MB6375.namprd11.prod.outlook.com ([fe80::8b5:ae20:1c12:421b]) by DS0PR11MB6375.namprd11.prod.outlook.com ([fe80::8b5:ae20:1c12:421b%7]) with mapi id 15.20.5417.026; Tue, 12 Jul 2022 13:51:11 +0000 Message-ID: <2c6a4a61-e6c8-0487-8d29-dc3fbb90bbe2@intel.com> Date: Tue, 12 Jul 2022 15:51:04 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.11.0 Subject: Re: [PATCH 1/2] lib/string_helpers: Introduce strsplit_u32() Content-Language: en-US To: Andy Shevchenko CC: =?UTF-8?Q?P=c3=a9ter_Ujfalusi?= , "Andy Shevchenko" , Mark Brown , "ALSA Development Mailing List" , Takashi Iwai , Jaroslav Kysela , , Pierre-Louis Bossart , Hans de Goede , Ranjani Sridharan , "Linux Kernel Mailing List" , Liam Girdwood , Kai Vehmanen , Bard Liao References: <6c8e4104-2239-a188-649d-585f059cabdd@intel.com> From: Cezary Rojewski In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR3P281CA0020.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:1c::21) To DS0PR11MB6375.namprd11.prod.outlook.com (2603:10b6:8:c9::21) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 02a86f81-b28d-44de-d912-08da640d9466 X-MS-TrafficTypeDiagnostic: CH2PR11MB4376:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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The IPC handlers for AudioDSP >> drivers are expecting payload in u32s. >> >> // u32 **tkns, size_t *num_tkns as foo() arguments >> // u32 *ints, int nints as locals >> >> get_options(buf, 0, &nints); >> if (!nints) { >> ret = -ENOENT; >> goto free_buf; >> } >> >> ints = kcalloc(nints + 1, sizeof(*ints), GFP_KERNEL); >> if (!ints) { >> ret = -ENOMEM; >> goto free_buf; >> } >> >> get_num_options(buf, nints + 1, ints, sizeof(*ints)); >> >> *tkns = ints; >> *num_tkns = nints; >> >> No additional operations in between. The intermediate IPC handler can later >> refer to the actual payload via &tkns[1] before passing it to the generic >> one. >> >> Casting int array into u32 array does not feel right, or perhaps I'm missing >> something like in the doc case. > > C standard. > > int to unsigned int is not promoted. And standard says that "The rank of any > unsigned integer type shall equal the rank of the corresponding signed integer > type, if any." > > I don't know why one needs to have an additional churn here. int and unsigned > int are interoperable with the adjustment to the sign when the other argument > is signed or lesser rank of. I still believe that casting blindly is not the way to go. I did explicitly ask about int vs u32, not int vs unsigned int. Please note that these values are later passed to the IPC handlers, and this changes the context a bit. If hw expects u32, then u32 it shall be. Please correct me if I'm wrong, but there is no guarantee that int is always 32bits long. What is guaranteed though, is that int holds at least -/+ 32,767. Also, values larger than INT_MAX are allowed in the IPC payload. Regards, Czarek