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=_261411A7-0D54-441B-B2D1-000A1F6ED635"; protocol="application/pgp-signature"; micalg=pgp-sha256 From: "H. Nikolaus Schaller" In-Reply-To: <20160822224247.vdh3plda6dxelvzw@earth> Date: Tue, 23 Aug 2016 09:28:40 +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: <20160818202900.hyvm4hfxedifuefn@earth> <20160819052125.ze5zilppwoe3f2lx@earth> <53A846F1-33E5-48C3-B3A6-DB251661CDD5@goldelico.com> <20160820143405.04303834@lxorguk.ukuu.org.uk> <20160822203947.ksxwnvzhc3tpnnx7@earth> <20160822224247.vdh3plda6dxelvzw@earth> To: Sebastian Reichel Sender: linux-kernel-owner@vger.kernel.org List-ID: --Apple-Mail=_261411A7-0D54-441B-B2D1-000A1F6ED635 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Hi, > Am 23.08.2016 um 00:42 schrieb Sebastian Reichel : >=20 >> I am not a specialist for such things, but I think you have three >> options to connect bluetooth: >>=20 >> 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) >>=20 >> 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. >>=20 >> BTW: the Wi2Wi W2CBW003 chip comes in two firmware variants: one for = UART and >> one for USB. So they are also not exchangeable. >=20 > Yes, let's ignore option c). > I'm talking about UART only. If the > chip has native USB support, then that's a different driver. Exactly. >=20 >> 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. >=20 > Well for some chips there is not native USB support. But my scenario > was about development. Let's say I have a serial-chip and I want to > develop a driver for it. It would be nice if I can develop the > driver with a USB-UART Yes it would be nice, but is this a thing with significant practical = relevance? Usually you have to write drivers for a complete device where the slave chip is already wired up to a SoC-UART. Sometimes you can get a bare chip where you can connect to an USB-UART. But someone has to design that piece of special hardware for you. If you are really lucky there is an evaluation board. And in that case I would use a RasPi or BeagleBone and tie up directly to some SoC-UART instead of using an intermediate USB-UART adapter. Because it is more close to timing relations to the final SoC based = design. > and then use it on my embedded system. >=20 > There are usb-serial devices, which could benefit from support > btw. I would find it really useful, if the Dangerous Prototype's > Bus Pirate would expose native /dev/i2c and /dev/spi and it's > based on FT232. Oh, that is an interesting device I didn't know yet. >=20 >> So to me it looks as if you need to develop different low-level >> drivers anyways. >=20 > No. You say, that option b) is irrelevant and assume, that every > serial chip also has native USB support. I just assume that b) is rarely used because there are alternatives. Although it would be a nice option. Anyways, while following the discussion this is not the most important facet of the overall topic. BR, Nikolaus --Apple-Mail=_261411A7-0D54-441B-B2D1-000A1F6ED635 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----- iQIcBAEBCAAGBQJXu/spAAoJEIl79TGLgAm6sQcP/R0xqIYmPEXN2uMshzvZ4kpa JIQxz6W2E8bNdcBF4CV7yBUBDg4daQ1mUMtOqPyjOoCTpysdBHcqwdBnkGXCjXnm fkhBrg7iGgBVNbJEEfTm+0x+xPvpysjY2wm2uaqeqgsrLOFqoDNYs+WsM0JSNNzJ yNfLrTB9/RwGhIfNR5a1oBPYlDYBRQmZqrPhSbFEfz8q+6OBNpkzp8yRkhr9K3A1 pq6Z9OIdWVgUHbvJXr632l1j/gmEXOnrjtOUfXNDwpiCfNYHCtHozvkTlXwFKlEC F9t5E6b0Gwl23l5wTUEFjDJObcf8iPu7ikRt4natAHjMNSTzDQl+rUOfI2BW3CWS CWuRF96YPuyxx11/SerpxwFKRMs51NgD+1MhgBuRtmaFJFcnPlhSzdjncCE8e3I/ IZ9CfguZBnMl7JN5v4Hv7Ex++YRV9IKoYSvMmabefJkp7E/fMH9MY3B9aaakWrHo IyRR4/bRoTJZrHBjsFYhQP0drr1uXcXSRaOEqMsrQV9RMh1deLzXPC7Dp2XbPDYC hrcSmHM6VDnlFJNNao60g4d+sS1o5P1JWsABtxVukSSoM3t3/zbQx7VORNLxQJSx mvs0vz4hLMwV4bXnWzpUJvOW2LmLlT24CG7eTus8vyJfVcD/ZGQw+ToByfxh/j3D 9LjcAGrqiSoZ50rieIMc =Tt6A -----END PGP SIGNATURE----- --Apple-Mail=_261411A7-0D54-441B-B2D1-000A1F6ED635--