From mboxrd@z Thu Jan 1 00:00:00 1970 From: Austin S Hemmelgarn Date: Thu, 24 Sep 2015 16:17:04 +0000 Subject: Re: No more new fbdev drivers, please Message-Id: <56042200.5070006@gmail.com> MIME-Version: 1 Content-Type: multipart/mixed; boundary="------------ms020307070306080802090908" List-Id: References: <5603EC15.9090605@ti.com> <20150924144621.40e26f0a@free-electrons.com> <560414EB.508@gmail.com> <20150924155912.GW3383@phenom.ffwll.local> In-Reply-To: <20150924155912.GW3383@phenom.ffwll.local> To: Thomas Petazzoni , Tomi Valkeinen , Greg Kroah-Hartman , linux-fbdev , DRI Development , Sudip Mukherjee , Teddy Wang , =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= , Laurent Pinchart , Dave Airlie , "linux-kernel@vger.kernel.org" , Arnaud Patard This is a cryptographically signed message in MIME format. --------------ms020307070306080802090908 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-24 11:59, Daniel Vetter wrote: > On Thu, Sep 24, 2015 at 11:21:15AM -0400, Austin S Hemmelgarn wrote: >> On 2015-09-24 08:46, Thomas Petazzoni wrote: >>> Hello, >>> >>> On Thu, 24 Sep 2015 15:27:01 +0300, Tomi Valkeinen wrote: >>> >>>> fbdev is (more or less) maintained, but it's a deprecated framework.= All >>>> new Linux display drivers should be done on DRM. >>>> >>>> So let's not add any more new fbdev drivers. >>>> >>>> I will continue to maintain the current fbdev drivers, and I don't m= ind >>>> adding some new features to those current drivers, as long as the am= ount >>>> of code required to add the features stays sensible. >>>> >>>> I see we have three fbdev drivers in staging: xgifb, fbtft and sm750= fb, >>>> and the question is what to do with those. >>>> >>>> xgifb was added in 2010, and is still in staging. >>>> >>>> fbtft looks like maybe some kind of framework on top of fbdev, with >>>> fbtft specific subdrivers... I didn't look at it in detail, but my g= ut >>>> says "never". >>> >>> fbtft mainly drives some very simple I2C-based or SPI-based displays,= >>> and DRM is I believe overkill for such displays. Last time I talked >>> with Laurent Pinchart about such drivers, I believe he said that such= >>> simple drivers could probably continue to use the fbdev subsystem. >> I have to agree, using DRM _really_ doesn't make sense for these, the >> devices in question are (AFAIK) simple I2C or SPI connected frame-buff= er >> chips that are hooked up to equally simple TFT displays. There's no 3= d >> acceleration at all from what I can tell, there's _very_ limited 2d >> acceleration, and most of the stuff that the DRM framework provides >> call-backs for would have to be done on the CPU anyway. On top of tha= t, >> it's targeted at small embedded systems with limited memory, and the D= RM >> framework is by no-means lightweight (TBH, fbdev isn't really either, = but >> it's much more light weight than DRM). > > See my other mail, but you can write very simple drm drivers. And if > there's really a bloat problem for small systems we can add Kconfig kno= bs > to throw out everything not needed for simple drivers. The only problem= > really is that everyone with such simple drivers doesn't even consider = drm > "because I don't have a desktop gpu" which is just silly - drm has beco= me > rather flexible. And that's essentially why writing simple drm drivers > still has a bit too much boilerplate, since no one yet bothered to add = a > bit of helper support needed. > Rather ironically, I got your other mail right after I sent this one. I = hadn't realized most of the points you made there (it's been a long time = since I looked at any drm related code (largely because I've had=20 absolutely 0 issues on my systems with it, which is a good thing :))).=20 I do think being able to compile out some of the drm stuff that isn't=20 used on a given system would be nice, and some good helper functions to=20 simplify writing basic drivers would be absolutely wonderful. As far as not considering it 'because I don't have a desktop GPU' goes,=20 I agree, that is silly, although for some people it may be 'because my=20 chip doesn't do any "rendering"', which brings up the rather complicated = discussion of what constitutes a GPU and what 'rendering' means. --------------ms020307070306080802090908 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Brgwgga0MIIEnKADAgECAgMRLfgwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwOTIxMTEzNTEzWhcNMTYwMzE5MTEzNTEzWjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz ZXIxIzAhBgkqhkiG9w0BCQEWFGFoZmVycm9pbjdAZ21haWwuY29tMSIwIAYJKoZIhvcNAQkB FhNhaGVtbWVsZ0BvaGlvZ3QuY29tMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA nQ/81tq0QBQi5w316VsVNfjg6kVVIMx760TuwA1MUaNQgQ3NyUl+UyFtjhpkNwwChjgAqfGd LIMTHAdObcwGfzO5uI2o1a8MHVQna8FRsU3QGouysIOGQlX8jFYXMKPEdnlt0GoQcd+BtESr pivbGWUEkPs1CwM6WOrs+09bAJP3qzKIr0VxervFrzrC5Dg9Rf18r9WXHElBuWHg4GYHNJ2V Ab8iKc10h44FnqxZK8RDN8ts/xX93i9bIBmHnFfyNRfiOUtNVeynJbf6kVtdHP+CRBkXCNRZ qyQT7gbTGD24P92PS2UTmDfplSBcWcTn65o3xWfesbf02jF6PL3BCrVnDRI4RgYxG3zFBJuG qvMoEODLhHKSXPAyQhwZINigZNdw5G1NqjXqUw+lIqdQvoPijK9J3eijiakh9u2bjWOMaleI SMRR6XsdM2O5qun1dqOrCgRkM0XSNtBQ2JjY7CycIx+qifJWsRaYWZz0aQU4ZrtAI7gVhO9h pyNaAGjvm7PdjEBiXq57e4QcgpwzvNlv8pG1c/hnt0msfDWNJtl3b6elhQ2Pz4w/QnWifZ8E BrFEmjeeJa2dqjE3giPVWrsH+lOvQQONsYJOuVb8b0zao4vrWeGmW2q2e3pdv0Axzm/60cJQ haZUv8+JdX9ZzqxOm5w5eUQSclt84u+D+hsCAwEAAaOCAVkwggFVMAwGA1UdEwEB/wQCMAAw VgYJYIZIAYb4QgENBEkWR1RvIGdldCB5b3VyIG93biBjZXJ0aWZpY2F0ZSBmb3IgRlJFRSBo ZWFkIG92ZXIgdG8gaHR0cDovL3d3dy5DQWNlcnQub3JnMA4GA1UdDwEB/wQEAwIDqDBABgNV HSUEOTA3BggrBgEFBQcDBAYIKwYBBQUHAwIGCisGAQQBgjcKAwQGCisGAQQBgjcKAwMGCWCG SAGG+EIEATAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLmNhY2Vy dC5vcmcwMQYDVR0fBCowKDAmoCSgIoYgaHR0cDovL2NybC5jYWNlcnQub3JnL3Jldm9rZS5j cmwwNAYDVR0RBC0wK4EUYWhmZXJyb2luN0BnbWFpbC5jb22BE2FoZW1tZWxnQG9oaW9ndC5j b20wDQYJKoZIhvcNAQENBQADggIBADMnxtSLiIunh/TQcjnRdf63yf2D8jMtYUm4yDoCF++J jCXbPQBGrpCEHztlNSGIkF3PH7ohKZvlqF4XePWxpY9dkr/pNyCF1PRkwxUURqvuHXbu8Lwn 8D3U2HeOEU3KmrfEo65DcbanJCMTTW7+mU9lZICPP7ZA9/zB+L0Gm1UNFZ6AU50N/86vjQfY WgkCd6dZD4rQ5y8L+d/lRbJW7ZGEQw1bSFVTRpkxxDTOwXH4/GpQfnfqTAtQuJ1CsKT12e+H NSD/RUWGTr289dA3P4nunBlz7qfvKamxPymHeBEUcuICKkL9/OZrnuYnGROFwcdvfjGE5iLB kjp/ttrY4aaVW5EsLASNgiRmA6mbgEAMlw3RwVx0sVelbiIAJg9Twzk4Ct6U9uBKiJ8S0sS2 8RCSyTmCRhJs0vvva5W9QUFGmp5kyFQEoSfBRJlbZfGX2ehI2Hi3U2/PMUm2ONuQG1E+a0AP u7I0NJc/Xil7rqR0gdbfkbWp0a+8dAvaM6J00aIcNo+HkcQkUgtfrw+C2Oyl3q8IjivGXZqT 5UdGUb2KujLjqjG91Dun3/RJ/qgQlotH7WkVBs7YJVTCxfkdN36rToPcnMYOI30FWa0Q06gn F6gUv9/mo6riv3A5bem/BdbgaJoPnWQD9D8wSyci9G4LKC+HQAMdLmGoeZfpJzKHMYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTI0MTYxNzA0WjBPBgkq hkiG9w0BCQQxQgRAWOjejYwBMw/vZWcsOi6JWRjSbKdWwfKUXdrWdGDVYaMHa9Ct/O/xXusp FazlT7Np4BM0kwJ2NV9rzk0ZmiZ3bjBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgAG96DYi68cWznWcxTBsMU5sdu2A5ytGbHsZqE+N9ASJ1eqdBWz qEzR4f1RRWt02UB+zPwfAhNAsTu/J8DdhJagF7g4l8BDLT5cWDtipkz8ArfjGbTai/PGdq/D yR2l8OT1N3rMsLw3tH2+k1Ihcm840K9g5h2LNx1RUlm54v5qF+4vxBHxQqCJwbDh1llvm1ma GYlCaX5+Fi18lEPCSQe0XVD095zQMHPve82TXiOR64Cnz1iW8mB7a3/SmP/Dj1COdVgGluQh 1wpT6HulAU5zqsDC4j8KdubEVxhtwXfijRwyuW0OPVsecHcRTRRLQOlvz8YTXyjkGyIf4BpX eYA9MG90izMiEkf1rLYpHSl771x0HY2Ry3oJ76mV+SYbaGBdnpYdHiZrVQQFEoQiJ/9UoRD4 gIAwAwFfT4loRupCBkEBk0Hl+DzbfAk4qrr4tehUMFYEfFRyUZui9JRvcxkokjL6NTWfJTVx +A/vWw9rY7f46+O8VBgWcO3cEXm/LA9vXP8+sFKFqGIEs/JuIQ62uAehR51tC2ZoC6z7FQe5 KsbYDaZLzw0IlSJNwPtw+ASvxELvS6YFy7KAXKQsuvdquXnxJce0PykV3azy4bLIF/yMOU6L XfyaVnyLZksVuHCeywv6JXKfWx8LNlwvJOG0SYz1vlV6z/xQ5AEwry20rwAAAAAAAA== --------------ms020307070306080802090908--