Hi Sebastian, > Am 22.08.2016 um 22:39 schrieb Sebastian Reichel <sre@xxxxxxxxxx>: > > Hi, > > 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 <gnomes@xxxxxxxxxxxxxxxxxxx>: >>>> 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). >>> >>> 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. >> >> Not necessarily. >> >> 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). >> >> This does not require I2C to be able to handle SPI or vice versa or provide a common API. > > 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). > >> 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. > > 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
Attachment:
signature.asc
Description: Message signed with OpenPGP using GPGMail
