From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 82C2C93C for ; Wed, 19 Jul 2017 07:59:37 +0000 (UTC) Received: from twosheds.infradead.org (twosheds.infradead.org [90.155.92.209]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id DC7BCAD for ; Wed, 19 Jul 2017 07:59:36 +0000 (UTC) Message-ID: <1500451171.19151.13.camel@infradead.org> From: David Woodhouse To: Jiri Kosina , Linus Torvalds In-Reply-To: References: <20170619103912.2edbf88a@gandalf.local.home> <20170619152055.GM3786@lunn.ch> <20170619122651.57ba27c4@gandalf.local.home> <20170624081411.58b4fb6a@vento.lan> <20170624140659.GM4875@lunn.ch> <20170624184216.2ffd4a96@gandalf.local.home> <20170624232140.GA27473@lunn.ch> <20170624234805.GT10672@ZenIV.linux.org.uk> <20170625012913.GC27473@lunn.ch> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-qLjMcMcS9KWhpCwujnaH" Date: Wed, 19 Jul 2017 09:59:31 +0200 Mime-Version: 1.0 Cc: Mauro Carvalho Chehab , ksummit Subject: Re: [Ksummit-discuss] [TECH TOPIC] printk redesign List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-qLjMcMcS9KWhpCwujnaH Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2017-06-26 at 10:46 +0200, Jiri Kosina wrote: > On Sat, 24 Jun 2017, Linus Torvalds wrote: >=20 > >=20 > > >=20 > > > It is how the embedded world operates, RS232, or now more often, RS23= 2=C2=A0 > > > with a built in USB-RS232 converter, so you use USB on the host. > > I'm not saying that serial lines shouldn't be an option. > >=20 > > But for a *large* user base, they simply aren't. > >=20 > > On regular PC's, it's often not an option any more. Even in the data > > center, it's often not an option any more. > I don't really agree here. Yes, the mid-to-hig-end servers don't probably= =C2=A0 > contain the actual UART chip any more, but the vast majority of those hav= e=C2=A0 > somehting that's emulated in firmware, and actually do have a serial=C2= =A0 > console line connector (not the 9-pin one, but rather RJ-45 with either= =C2=A0 > Cisco or Yost pinout), which is then connected into serial-over-TCP=C2=A0 > concentrator box, exposing the serial console over telnet (or some=C2=A0 > proprietary client application). This is seen in DCs quite frequently. >=20 > Even machines that have very good IPMI support still ship with this. Yeah, we definitely still have a "serial console" in the data centre, even if it's not actually RS232 any more. Or indeed "serial". You want to catch those failures where even kdump doesn't manage to give you a viable report of the original crash? You'd better be watching... Even on regular PCs we have the USB debug ports which can serve the same purpose. But still, we're talking about printk being used for its original $DEITY-intended purpose for debugging and diagnostic data. Not for the random "hey, here's a channel I can abuse to send data up to userspace" stuff. I heartily agree with Steven when he says that "printk is used too freely". --=-qLjMcMcS9KWhpCwujnaH Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCDzUw ggSvMIIDl6ADAgECAhEA4CPLFRKDU4mtYW56VGdrITANBgkqhkiG9w0BAQsFADBvMQswCQYDVQQG EwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRU UCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MB4XDTE0MTIyMjAw MDAwMFoXDTIwMDUzMDEwNDgzOFowgZsxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1h bmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMUEw PwYDVQQDEzhDT01PRE8gU0hBLTI1NiBDbGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBF bWFpbCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAImxDdp6UxlOcFIdvFamBia3 uEngludRq/HwWhNJFaO0jBtgvHpRQqd5jKQi3xdhTpHVdiMKFNNKAn+2HQmAbqUEPdm6uxb+oYep 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