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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 BB0F3C43219 for ; Tue, 30 Apr 2019 12:11:37 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 616F2205ED for ; Tue, 30 Apr 2019 12:11:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 616F2205ED Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=secunet.com Authentication-Results: mail.kernel.org; spf=fail smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.91) (envelope-from ) id 1hLRbe-0008Ik-AZ; Tue, 30 Apr 2019 08:11:30 -0400 Received: from a.mx.secunet.com ([62.96.220.36]) by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1hLRbb-0008IW-E0 for kernelnewbies@kernelnewbies.org; Tue, 30 Apr 2019 08:11:27 -0400 Received: from localhost (localhost [127.0.0.1]) by a.mx.secunet.com (Postfix) with ESMTP id CC9B020097 for ; Tue, 30 Apr 2019 14:11:25 +0200 (CEST) X-Virus-Scanned: by secunet Received: from a.mx.secunet.com ([127.0.0.1]) by localhost (a.mx.secunet.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CPV651aU-xqt for ; Tue, 30 Apr 2019 14:11:24 +0200 (CEST) Received: from mail-essen-01.secunet.de (mail-essen-01.secunet.de [10.53.40.204]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by a.mx.secunet.com (Postfix) with ESMTPS id 9D894201DA for ; Tue, 30 Apr 2019 14:11:24 +0200 (CEST) Received: from [10.182.7.62] (10.182.7.62) by mail-essen-01.secunet.de (10.53.40.204) with Microsoft SMTP Server (TLS) id 14.3.439.0; Tue, 30 Apr 2019 14:11:24 +0200 Subject: Re: debugfs question ... To: References: <009001d4ff4a$2ac6a030$8053e090$@metamail.co> From: Martin Christian Openpgp: preference=signencrypt Autocrypt: addr=martin.christian@secunet.com; prefer-encrypt=mutual; keydata= xsFNBFpYwm8BEAC0Fxsr95okvqmOU0wYqdmFODEnTKfivkkDJk7iJMATxMGcMqr8X2KBwJO1 meTqAR9LnsB4OTzbznMdLEqDd1JvFQ4a5Da+lMn55yNmPfIYMo6NW5o5VkyVQOqa8iHZuNrv 14uqsrm+Rjl/HRgTu+11xqB1SWXrrKH4wMHArQ1A8FgXTcfrLk/u1gC2fGLt2/EhsU7hjXlt PkTQUAigjV0SYAUya9Ux5elSuq4VBrBgkBuZZi3bvlzIFOQ+IVsxdz0w6JbexPEF8u/AKdLy SuWJCpjo2QLx0t87XCvQCImzyGGJU2UEFkDR9T99pd072e0NvKSwCs9LCciimZEWrXWSbfwo CKsdFsP6JtETYUt/gU8hLhqDL6vawuDxuTI1Ztm5Ij8o9NazJv0BEcgTKc1tv7BPf+kEfSsJ 3GgwRXWtotlX8y/pClhy6XpXk4qglmSLW/Y6QsCK0sd729GMFDtAKzZoRMCZL7+w1YY5ziGm +4YDjPP4Qil3C14OSpjyyHLX+dfyTkR3YzVeT6bvi8JfA6JeEKgh+p9YB/e9TL3d0e86iDg7 fHIMfEk/wc81tRUUnLPwP+UJU7Nmd++LytEme1Ubi0Pt853B3ZAUU/YSRFr/g+OswFy3H0Xo K/22BUzNQkGx3bI3c+eefVvdp4IyEH0Csk3emdbvrb1whGHUAwARAQABzS9NYXJ0aW4gQ2hy aXN0aWFuIDxtYXJ0aW4uY2hyaXN0aWFuQHNlY3VuZXQuY29tPsLBfQQTAQgAJwUCWljCbwIb AwUJA7KVAAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRAjtu88DNmcVpz/D/9c4NlAqbPU rFUKIROdaBV8gkKhIW+z/GSWGCkr2AP6JKDXBrd+tv/WgAkBUB1PmUJ39jnU1jVI97waiD5x CmFlY0oprW2CIss0THKbt7YdpMlQw5niwH/SKTwEyQCCasGQIipKapWvZeelkijioSYSlsew vAR/lXjZ2qAy8GL+CpmbuFTl6LIui3LJVuRs5CK9+G2AehgY1Y2s/N67KmFtXhyDxmFL80uP US3TvXpZxzIbZgctSUCUcmrc4oocwDG188mGelBO7N91WUuuoAWbRZ9Xe/CDVQirgficjJNg WLdxVyC2Q9s43To97QiAB4OUYYVvxOp/7smBCGZzUk0cuMjhSVSKoXbv9+OFFiLNoUs3Qag6 7XSUTYaxvCIqUPEI5Qibj4Rg2P5w5GBIct5DKZf6k7ivIxdTyRe5kWEYr4riKij2mA8AeurZ Swkj04hZrjI7/MnLv63Zah64Gb9eU+3s5IX6sB72C+AB5hm0qEnDivCAXeuFZR24ISZOXk5M fN/H0IgeKAZyRokZ75gzRGYQb4WVpxTrZ4Ecpb8RBlazQjd+XuACOSrpC0P7A5Qnbgw3aISB vSboTw9vQS2wkpYqZDAoxHELkqr2GEaGfr3/RSWw6NQ0DM8pO3xl37BqBeXTjpHzJ+ExQwLt ewqeez1g9uqXE9owO5c20gFkFc7BTQRaWMJvARAA069CF4uc+GkbY9MsdxbWPE7Gw9FSRI+f 5+Y8FbwfgB1BL82XlDezE7nTnHFdxJwuvAaXn+PJ4mhXYuoHvP2UxYvC3OmoxubgsiW3QyKa Z6J6+D2WNZIZJpWB8G5pPnxbtVmgh8x0lBnTWDto4EsgruxO1X+YBojmI06m8De8Z/meTOR2 RAYXhmw5Vy6iUf8GD8bhDHLXPwg8Ofsyc0LfYcA0M+hJ4TO0r3VXnJzbMATAQcw0fgscWTHl OOWqfIAb493mFywiINGqurYGzzyz8GqhZuu8Qrvn7sh8eMP8Ryre9CwQ74DyVeIUn1N88Ax/ dIaqwnCuJuTfGFdhZnAVw2EfRaBIYm3FgxvRCe+QEH5KuJ7RZI14c7v0Ej7I3AigXRgcAvSy +AOQOO+3z/K6ACFJz5zmyJ+Xduu4Gqd5LNGz0VXG7dsQ6BDNHechdHmPdDS4WYONCzkeHDtC tGclvUuslu7ZyHS5ivDNhXtWGNMgRjBID9/RNbpVt/e0J4rASIFlRbmQ8Hls6GEI6e7Adg5Z Cw+tmx1lXn+87NBfwjJcbv9WxTBb8o8ek8jJsyC5hd5kqfosy3Gqfi3hVpZXOkT3v2/XyxFM A0Kl5Ec+oUaEZYZ16m+rSYmHPuAu2lvyiuCNP45lSSYOjsWl5N2Xfyh7pHnt9rKzxgRzwdvi 98sAEQEAAcLBZQQYAQgADwUCWljCbwIbDAUJA7KVAAAKCRAjtu88DNmcVkZoD/4+r/SY6oSz jEZsTm6y1IOEdRLpohgkWl2T0oZ1H0aM22B4PQuFejhP7PDvsPye33YJ3z+Tbf7uVEPUtKdb uetSOLYDY59wi9ye8RsVyGkCTgK50QlzJwCbw3a4w2KmJL9OmNnHsj5u1Ms6XUdzILY31jTX kjaJgsAMDgY/KU+nzPqMVuQny2Ns4X/dL4tAgNsBMQO0A0utQ3cxD9VSiBb807wAcx2oYyVx GWwbuA80D9IH07x/Jyzgt5mBjTG60TW9/7hP1cAsLZaApFlbsPwRYNfVo8+poNFREfNWLYWk nPoaEKf+NAB3O/6QFFo6CSNFjKbfhqktGg6mJ9qmYdbLnNFcoXWXlIHMMSrVub+QALujf+6K Ajzhn0yake00vugbzPx1N1CthJD6RWyY89Zc/X+1OFl+7iFbPFC1+G2j1FrPtj+0P8Gw4N+P u4hBC2IC0RDFfK634LW92kWOJu6JjVZpbsiq5ZxNW+4J8WB3/hErsIdplW3LKWyv7RG8MnTM 9Gz/v4WdhbUCr203Fmn8RnGzFbPgTfDKSBe3gLm6QW/JhnJURECLBV3aPmPA3wl2hcozZacj SUYHd/Jhjw1/TKmxZXvD8E99XY5CqV+XchNshryuqF0fq9jQfv0spdSlX88j8Q0W1mPHEqGx 7XZ1NLfDSFwlysJFxJtzhRuxZQ== Message-ID: <531b212a-fb20-e2f2-f052-66e37fc5ba68@secunet.com> Date: Tue, 30 Apr 2019 14:11:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <009001d4ff4a$2ac6a030$8053e090$@metamail.co> X-EXCLAIMER-MD-CONFIG: 2c86f778-e09b-4440-8b15-867914633a10 X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============3180212116423499260==" Errors-To: kernelnewbies-bounces@kernelnewbies.org --===============3180212116423499260== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Z1KVDMjAENX17igj5wYI8U8rh1VoOCqsJ" --Z1KVDMjAENX17igj5wYI8U8rh1VoOCqsJ Content-Type: multipart/mixed; boundary="0fqvY4OHMhiQwMnACDK1XXmDd8h85NZc7"; protected-headers="v1" From: Martin Christian To: kernelnewbies@kernelnewbies.org Message-ID: <531b212a-fb20-e2f2-f052-66e37fc5ba68@secunet.com> Subject: Re: debugfs question ... References: <009001d4ff4a$2ac6a030$8053e090$@metamail.co> In-Reply-To: <009001d4ff4a$2ac6a030$8053e090$@metamail.co> --0fqvY4OHMhiQwMnACDK1XXmDd8h85NZc7 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Hi, my guess is your are not returning EOF (=3D 0). User space expects a return value of 0 (EOF) to terminate reading. But your code will always return sizeof("Hello world\n"). A fix would be to not only increment ppos, but also check if it's already behind your data. Regards, Martin Am 30.04.19 um 13:45 schrieb rdq@metamail.co: > Greetings, >=20 > My I2C sensor driver has a debugfs entry for development purposes. > Everything works fine with the exception of the read operation. When 'c= at' > is used, the read operation is called repeatedly and indefinitely. If t= he > read() is changed to return 0 then, as expected, nothing is displayed. = >=20 > The pattern for the implementation is (AFAICT) right out of the book (= shown > below).=20 >=20 > What am I missing? Any thoughts much appreciated. >=20 > TAIA. >=20 > RDQ >=20 > static ssize_t sc031gs_reg_read_file(struct file *file, char __user > *user_buf, > size_t count, loff_t *ppos) > { > char *buf =3D 0; > ssize_t total =3D 0; > struct sc031gs_dev *sensor =3D file->private_data; > if (!sensor) > return -EINVAL; > if (*ppos < 0 || !count) > return -EINVAL; > buf =3D kmalloc(count, GFP_KERNEL); > if (!buf) > return -ENOMEM; > total =3D snprintf(buf,count,"Hello world\n"); > if (total >=3D 0) { > if (copy_to_user(user_buf, buf, total)) { > kfree(buf); > return -EFAULT; > } > *ppos +=3D total; > } > kfree(buf); > return total; > } >=20 >=20 > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >=20 --=20 Dipl.-Inf. Martin Christian Senior Berater Entwicklung Hardware secunet Security Networks AG Tel.: +49 201 5454-3612, Fax +49 201 5454-1323 E-Mail: martin.christian@secunet.com Ammonstra=C3=9Fe 74, 01067 Dresden www.secunet.com --0fqvY4OHMhiQwMnACDK1XXmDd8h85NZc7-- --Z1KVDMjAENX17igj5wYI8U8rh1VoOCqsJ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEcVMZ0aBmilTEqb/wI7bvPAzZnFYFAlzIO2oACgkQI7bvPAzZ nFZZPBAAlVw0RomHqTiXApY73umDui9o+yeLkB28v9i9/6LHfY49LVIcdOqZKRAK qQk68OVTbwYhbPpKKyX4cVIZ/29Fatzh1+nk3Z4+UQpSVCBGqxV9b7bw6m+nO030 YsryMt3OR6gKOQ80WiPZW5WGbLMoB43U6FnskDGxNVlXw5PvwGFvNRXGBtqcImUh CaOuTavCGOgtFIQk1YWCTWdvf+HDGs8rYUmVbCUCziKJqUhW7ceVowwZuOoi5Gpk tKFt4TDOwjswtFw9Lx9vy+Kmome/LYKeEU1bdok9SOFCjKqLm4J9Fz+RkWQRlhAm hT39SJbzbQO5tNqNIsFTMb7OFft6rC1x/MDfXkrPT1SHB3ZBF/ZXBfOM2O3H8wRp ZLB1sT7HCayf+hfpL0fcCeq7RyXG/z+ewR0NdNUTiJz6ZYkbCELBwIGwDmT8WOZd ldfoztstY1uhRfGpmanWeCuAtAPlJXSgX+TZo9eYHLU7cNdWCHbn1SM4hDjG79fW MRjfgPXeSIrrcjz3rEdDePRR0mFx0V4lDKcpogIpR1eiRiA+qVVZKSY3e2rk+F+P RccTSSdZNZiAhYzkjUzwYCZIs27IUst0710WzcPtGtKPGLCui7uN82+7fxq+JZlv /zCFBqzr/jVkZkX2OZ0tzoXp9fl12XHOL5RZSRJphwZwoRPPYHo= =OOLL -----END PGP SIGNATURE----- --Z1KVDMjAENX17igj5wYI8U8rh1VoOCqsJ-- --===============3180212116423499260== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies --===============3180212116423499260==--