Return-Path: Subject: Re: [RFC PATCH 0/3] UART slave device bus Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Content-Type: multipart/signed; boundary="Apple-Mail=_B8E38301-1A40-45ED-B7E9-652C33E3B2ED"; protocol="application/pgp-signature"; micalg=pgp-sha256 From: "H. Nikolaus Schaller" In-Reply-To: <20160822203947.ksxwnvzhc3tpnnx7@earth> Date: Mon, 22 Aug 2016 23:23:26 +0200 Cc: One Thousand Gnomes , Oleksij Rempel , Rob Herring , Greg Kroah-Hartman , Marcel Holtmann , Jiri Slaby , Pavel Machek , Peter Hurley , NeilBrown , Arnd Bergmann , Linus Walleij , "open list:BLUETOOTH DRIVERS" , "linux-serial@vger.kernel.org" , "linux-kernel@vger.kernel.org" Message-Id: References: <20160818011445.22726-1-robh@kernel.org> <20160818202900.hyvm4hfxedifuefn@earth> <20160819052125.ze5zilppwoe3f2lx@earth> <53A846F1-33E5-48C3-B3A6-DB251661CDD5@goldelico.com> <20160820143405.04303834@lxorguk.ukuu.org.uk> <20160822203947.ksxwnvzhc3tpnnx7@earth> To: Sebastian Reichel List-ID: --Apple-Mail=_B8E38301-1A40-45ED-B7E9-652C33E3B2ED Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Hi Sebastian, > Am 22.08.2016 um 22:39 schrieb Sebastian Reichel : >=20 > Hi, >=20 > On Sun, Aug 21, 2016 at 09:50:57AM +0200, H. Nikolaus Schaller wrote: >>> Am 20.08.2016 um 15:34 schrieb One Thousand Gnomes = : >>>> What it is not about are UART/RS232 converters connected through = USB or virtual >>>> serial ports created for WWAN modems (e.g. /dev/ttyACM, = /dev/ttyHSO). Or BT devices >>>> connected through USB (even if they also run HCI protocol). >>>=20 >>> It actually has to be about both because you will find the exact = same >>> device wired via USB SSIC/HSIC to a USB UART or via a classic UART. = Not is >>> it just about embedded boards. >>=20 >> Not necessarily. >>=20 >> We often have two interface options for exactly the sam sensor chips. = They can be connected >> either through SPI or I2C. Which means that there is a core driver = for the chip and two different >> transport glue components (see e.g. iio/accel/bmc150). >>=20 >> This does not require I2C to be able to handle SPI or vice versa or = provide a common API. >=20 > I don't understand this comparison. I2C and SPI are different > protocols, Yes, they are different on protocol level, but on both you transfer = blocks of data from/to a slave device which usually can be addressed. And for some chips they are just two = slightly alternative serial interfaces. > while native UART and USB-connected UART are both UART. I see what you mean, but kernel divides between directly connected UART = and USB-connected UART. drivers/usb/serial/ vs. drivers/tty/serial/ to implement two different groups of UARTs. Although on user space level = they are harmonized again. This is why I compare with i2c and spi. But each such comparison is not = perfect. Anyways, to me it looks as if everybody wants to make the solution work = for usb-uarts as well (although I still would like to see a real world use-case). >=20 >> And most Bluetooth devices I know have either UART or a direct >> USB interface. So in the USB case there is no need to connect >> it through some USB-UART bridge and treat it as an UART at all. >=20 > I think having support for USB-UART dongles is useful for > driver development and testing on non-embedded HW. Hm. I assume you mean the Bluetooth situation where both, embedded UART connected chips and USB dongles are available. I am not a specialist for = such things, but I think you have three options to connect bluetooth: a) SoC-UART <-> BT-Chip-UART-port b) USB-UART (FT232, PL2303 etc.) <-> BT-Chip-UART-port c) USB <-> BT-Chip-USB-port (not UART involved at all) Case c) IMHO means you anyways need a special USB driver for the BT-Chip = connected through USB and plugging it into a non-embedded USB port does not = automatically show it as a tty interface. So you can't use it for testing the UART = drivers. BTW: the Wi2Wi W2CBW003 chip comes in two firmware variants: one for = UART and one for USB. So they are also not exchangeable. Variant b) is IMHO of no practical relevance (but I may be wrong) = because it would mean to add some costly FT232 or PL2302 chip where a different firmware = variant works with direct USB connection. So to me it looks as if you need to develop different low-level drivers = anyways. BR, Nikolaus --Apple-Mail=_B8E38301-1A40-45ED-B7E9-652C33E3B2ED Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- iQIcBAEBCAAGBQJXu21PAAoJEIl79TGLgAm6koAP/0tKd2aB9CPnQCGP8697+8Tn NPDtFMHfEf6IGZBhpXASyoK2LSJWNXsvGOgUKiFx6iBSI5QqYSbBrBklDvlsme9X hlmRdnPa+bqypmjAfVpSQnIUzcnrYzOBpzNrh6nabknj7uChzB1uG3Zx0y1aBjFE UoluIf0gxVtv1nffvZyGA1Q9y07+kQJgusNMCDKvlgNjzcgpEhydTjNeDUmVm6x0 o++SSiTLiYgN15DKivt/onEe+9wkAdP7/cRHjnGcmopyuhDNEkN9GOrYbUP9b+vg I+rgu7tF/iekf1lQb65Gc659/XL+LH+Ubr3yTmf56xgGaqjRiGAs/8SgIacGJZKW vXAcdJ1iB5HSbb9bpcMIavNhM/SnH3LxGRgFubkjZarRU/ENWxPaspxwG4ZybX/5 j0tmX5zG8FxpIkQltxRpWdqrI5pg76KtJqPcB7CvWaELwQf+0I6rWgpu8eJsPsNa k74P++8usExoC6iMgUOO2VSinilQ38Vun5l+/saG3MpMbyCR1QCoeeDYaNIm3rNJ MwzPHfrNu1oIMQs6lqSb0pp9UP/pMFpRuOT23YoSLtXIBJUqSsMaD6J8CcDOaoG2 x7FwmN/dGuocXAt/8pboyfwwP3sDBwclYuZNegfATVOQcOdGBjtn3+z3olkcOv7x hALlhQoLetWpASHiw3ER =sjI0 -----END PGP SIGNATURE----- --Apple-Mail=_B8E38301-1A40-45ED-B7E9-652C33E3B2ED--