From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 811CAC433B4 for ; Mon, 12 Apr 2021 11:56:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 419D06102A for ; Mon, 12 Apr 2021 11:56:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240687AbhDLL5P (ORCPT ); Mon, 12 Apr 2021 07:57:15 -0400 Received: from mail.sch.bme.hu ([152.66.249.140]:25082 "EHLO mail.sch.bme.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240622AbhDLL5O (ORCPT ); Mon, 12 Apr 2021 07:57:14 -0400 Received: from mail-lf1-f47.google.com (209.85.167.47) by Exchange2016-1.sch.bme.hu (152.66.249.140) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2176.2; Mon, 12 Apr 2021 13:56:55 +0200 Received: by mail-lf1-f47.google.com with SMTP id x13so10783849lfr.2; Mon, 12 Apr 2021 04:56:55 -0700 (PDT) X-Gm-Message-State: AOAM532UEud3TMvdRESMd0e7mc6wuNRdnt6Lua2oCgdbrZ2AyRgn2Huy szzlBfXTB4Pu0u1Vqfwd3dKmZsmWqz+IkDn7jbE= X-Google-Smtp-Source: ABdhPJzsgMVtHC/qdZLmU9vS3FCbAZxt8qW14PudyfBvduxe1m6zO8ygByHAx6ugH6ci4saRoBTSy72geMB63zTb7CQ= X-Received: by 2002:ac2:5ccd:: with SMTP id f13mr16239768lfq.596.1618228614130; Mon, 12 Apr 2021 04:56:54 -0700 (PDT) MIME-Version: 1.0 From: =?UTF-8?B?QmVuY2UgQ3PDs2vDoXM=?= Date: Mon, 12 Apr 2021 13:56:42 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Usage of get_random_bytes() in i2c-cp2615 To: , Content-Type: text/plain; charset="UTF-8" X-Originating-IP: [209.85.167.47] X-ClientProxiedBy: Exchange2016-1.sch.bme.hu (152.66.249.140) To Exchange2016-1.sch.bme.hu (152.66.249.140) Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Normally, `cp2615_i2c_transfer.tag` is a random number that identifies a given request-reply pair (the chip sends its response with the same tag it got in the request). Currently, for the sake of ease, my driver sends its requests with a fixed tag of 0xDD for all requests. This defeats the purpose of the tag system. Should I use `get_random_bytes()` instead? My concerns are that generating a random value for each I2C transfer may lead to the entropy pool being used up, especially since - if I understand correctly - `get_random_bytes()` always generates 32 bit random words and discards any extra bytes if `length%4 != 0`, and I only need 1 byte each time.