Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753463AbaLUKUf (ORCPT ); Sun, 21 Dec 2014 05:20:35 -0500 Received: from mail.kernel.org ([198.145.19.201]:47289 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751111AbaLUKU3 (ORCPT ); Sun, 21 Dec 2014 05:20:29 -0500 Date: Sun, 21 Dec 2014 11:20:19 +0100 From: Sebastian Reichel To: NeilBrown Cc: Mark Rutland , One Thousand Gnomes , Peter Hurley , Arnd Bergmann , Greg Kroah-Hartman , Grant Likely , Jiri Slaby , GTA04 owners , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] TTY: add support for "tty slave" devices. Message-ID: <20141221102017.GA18161@earth.universe> References: <20141219235827.13943.45713.stgit@notabene.brown> <20141220000920.13943.22511.stgit@notabene.brown> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="T4sUOijqQbZv57TR" Content-Disposition: inline In-Reply-To: <20141220000920.13943.22511.stgit@notabene.brown> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --T4sUOijqQbZv57TR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Neil, On Sat, Dec 20, 2014 at 11:09:20AM +1100, NeilBrown wrote: > A "tty slave" is a device connected via UART. > It may need a driver to, for example, power the device on > when the tty is opened, and power it off when the tty > is released. How about (reads a bit easier to me, but I'm not a native speaker): Such a device may need its own driver, e.g. for powering it up on tty open and powering it down on tty release. > A "tty slave" is a platform device which is declared as a > child of the uart in device-tree: maybe make this into its own device class instead of making it a platform device? > &uart1 { > bluetooth { > compatible =3D "wi2wi,w2cbw003"; > vdd-supply =3D <&vaux4>; > }; > }; >=20 > The driver can attach to the tty by calling > tty_set_slave(dev->parent, dev, &slave_ops); this could be handled by the tty core if a custom tty slave device class is used (similar to spi_device for spi slaves or i2c_client for i2c slaves). > where slave_ops' is a set of interface that > the tty layer must call when appropriate. > Currently only 'open' and 'release' are defined. > They are called at first open and last close. > They cannot fail. >=20 > Signed-off-by: NeilBrown > --- > .../devicetree/bindings/serial/of-serial.txt | 4 + > drivers/tty/tty_io.c | 73 ++++++++++++++= +++++- > include/linux/tty.h | 16 ++++ > 3 files changed, 90 insertions(+), 3 deletions(-) >=20 > diff --git a/Documentation/devicetree/bindings/serial/of-serial.txt b/Doc= umentation/devicetree/bindings/serial/of-serial.txt > index 8c4fd0332028..fc5d00c3c474 100644 > --- a/Documentation/devicetree/bindings/serial/of-serial.txt > +++ b/Documentation/devicetree/bindings/serial/of-serial.txt > @@ -39,6 +39,10 @@ Optional properties: > driver is allowed to detect support for the capability even without th= is > property. > =20 > +Optional child node: > +- a platform device listed as a child node will be probed and can > + register with the tty for open/close events to manage power. > + Drop the Linux specific bits and add the requirement of a compatible value here. Suggestion: Optional child node: A slave device connected to the serial port. It must contain at least a compatible property with a name string following generic names recommended practice. > Example: > =20 > uart@80230000 { > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 0508a1d8e4cd..6c67a3fd257e 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -95,6 +95,7 @@ > #include > #include > #include > +#include > =20 > #include > =20 > @@ -110,6 +111,13 @@ > #define TTY_PARANOIA_CHECK 1 > #define CHECK_TTY_COUNT 1 > =20 > +struct tty_device { > + struct device dev; > + > + struct tty_slave_operations *slave_ops; > + struct device *slave; > +}; > + > struct ktermios tty_std_termios =3D { /* for the benefit of tty drivers = */ > .c_iflag =3D ICRNL | IXON, > .c_oflag =3D OPOST | ONLCR, > @@ -1825,6 +1833,17 @@ int tty_release(struct inode *inode, struct file *= filp) > __func__, tty->count, tty_name(tty, buf)); > tty->count =3D 0; > } > + if (tty->dev && tty->count =3D=3D 0) { > + struct tty_device *ttyd =3D container_of(tty->dev, > + struct tty_device, > + dev); > + if (ttyd->slave) { > + mutex_lock(&ttyd->dev.mutex); > + if (ttyd->slave) > + ttyd->slave_ops->release(ttyd->slave, tty); > + mutex_unlock(&ttyd->dev.mutex); > + } > + } > =20 > /* > * We've decremented tty->count, so we need to remove this file > @@ -2105,6 +2124,18 @@ retry_open: > goto retry_open; > } > clear_bit(TTY_HUPPED, &tty->flags); > + if (tty->dev && tty->count =3D=3D 1) { > + struct tty_device *ttyd =3D container_of(tty->dev, > + struct tty_device, > + dev); > + if (ttyd->slave) { > + mutex_lock(&ttyd->dev.mutex); > + if (ttyd->slave && > + ttyd->slave_ops->open) > + ttyd->slave_ops->open(ttyd->slave, tty); > + mutex_unlock(&ttyd->dev.mutex); > + } > + } > tty_unlock(tty); > =20 > =20 > @@ -3168,6 +3199,7 @@ struct device *tty_register_device_attr(struct tty_= driver *driver, > { > char name[64]; > dev_t devt =3D MKDEV(driver->major, driver->minor_start) + index; > + struct tty_device *tty_dev; > struct device *dev =3D NULL; > int retval =3D -ENODEV; > bool cdev =3D false; > @@ -3190,12 +3222,12 @@ struct device *tty_register_device_attr(struct tt= y_driver *driver, > cdev =3D true; > } > =20 > - dev =3D kzalloc(sizeof(*dev), GFP_KERNEL); > - if (!dev) { > + tty_dev =3D kzalloc(sizeof(*tty_dev), GFP_KERNEL); > + if (!tty_dev) { > retval =3D -ENOMEM; > goto error; > } > - > + dev =3D &tty_dev->dev; > dev->devt =3D devt; > dev->class =3D tty_class; > dev->parent =3D device; > @@ -3207,6 +3239,12 @@ struct device *tty_register_device_attr(struct tty= _driver *driver, > retval =3D device_register(dev); > if (retval) > goto error; > + if (device && device->of_node) > + /* Children are platform devices and can register > + * for various call-backs on tty operations. > + */ > + of_platform_populate(device->of_node, NULL, NULL, dev); > + > =20 > return dev; > =20 > @@ -3238,6 +3276,35 @@ void tty_unregister_device(struct tty_driver *driv= er, unsigned index) > } > EXPORT_SYMBOL(tty_unregister_device); > =20 > +int tty_set_slave(struct device *tty, struct device *slave, > + struct tty_slave_operations *ops) > +{ > + struct tty_device *ttyd =3D container_of(tty, struct tty_device, dev); > + int err; > + if (tty->class !=3D tty_class) > + return -ENODEV; > + if (ttyd->slave) > + err =3D -EBUSY; > + else { > + ttyd->slave =3D slave; > + ttyd->slave_ops =3D ops; > + err =3D 0; > + } > + return err; > +} > +EXPORT_SYMBOL_GPL(tty_set_slave); > + > +void tty_clear_slave(struct device *tty, struct device *slave) > +{ > + struct tty_device *ttyd =3D container_of(tty, struct tty_device, dev); > + > + WARN_ON(ttyd->slave !=3D slave); > + ttyd->slave =3D NULL; > + ttyd->slave_ops =3D NULL; > +} > +EXPORT_SYMBOL_GPL(tty_clear_slave); > + > + > /** > * __tty_alloc_driver -- allocate tty driver > * @lines: count of lines this driver can handle at most > diff --git a/include/linux/tty.h b/include/linux/tty.h > index 5171ef8f7b85..fab8af995bd3 100644 > --- a/include/linux/tty.h > +++ b/include/linux/tty.h > @@ -299,6 +299,22 @@ struct tty_file_private { > struct list_head list; > }; > =20 > +/* A "tty slave" device is permanently attached to a tty, typically > + * via a UART. > + * The driver can register for notifications for power management > + * etc. Any operation can be NULL. > + * Operations are called under dev->mutex for the tty device. > + */ > +struct tty_slave_operations { > + /* 'open' is called when the device is first opened */ > + void (*open)(struct device *slave, struct tty_struct *tty); > + /* 'release' is called on last close */ > + void (*release)(struct device *slave, struct tty_struct *tty); > +}; Something like the following would be really useful for remote devices, that can/must be woken up from idle states via an GPIO (e.g. the bluetooth chip from the Nokia N900): /* 'write' is called when data should be sent to the remote device */ void (*write)(struct device *slave, struct tty_struct *tty); The same kind of GPIO exists for waking up the host's UART chip from idle, but that can simply be implemented by incrementing the runtime usage of the tty_slave's parent device :) > +int tty_set_slave(struct device *tty, struct device *slave, > + struct tty_slave_operations *ops); > +void tty_clear_slave(struct device *tty, struct device *slave); > + > /* tty magic number */ > #define TTY_MAGIC 0x5401 -- Sebastian --T4sUOijqQbZv57TR Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJUlp7eAAoJENju1/PIO/qaHpwP/Ar4umPu5EZACQxUhIoDWkw7 eSJPycLetOVfZ00hqOWf3mpjflT41SmD+Q3uI1M6adQjPF3XIpS9lle3ayVPsk+S +BVVA/H3B8OYK5ppPCQ6TrEqSGiZI5BgCfoIZYZLFoAS9TJvs9lsENMjUK65IARx RTIfNn2lr/d1pnYTIU+lvPVQap/QEryGgW1pJn13wJGWzRlcluuAOAECcm2RrIqg wBhL47qRkThaDPsIuhFgpz130Pzw9r4k9fmzRQDPYKxigLvl//DGPFCA29kPw4W5 ITx/nRKG2g6CzY8i8jpy2yG9DGaTKi1AJsDg5Zf7bvTmF/tyxk3lglzw0GrYpfnE 1FsDW4TZTMDnOmA1fON+jA6Ms18a3eA2RLDP+/IfcqJspKLndxFwfnScxqKBPCYm qu+3gOsSt7Y43J37zNq++H6XOw3ULVFInVRc2+aYHdLSzhUpAsTT5m8RrpJhWb2r qR3iwLKWHUwwyh3LwyIz3ZSvODTaVtubog+BomatNRUOAe7zigGpl1KvQS5gjeND 3EXuqfQlnC1Yka3zCR4VEBVonYLdwDW/Dox9h1RL1gSQdP7DJdKjeqqr0VwPnxwn SOdWJ5gySX5lDGyMIf8a+OMK3MDDPMg3tuyY3Q8PBZbtGZ3IpiiurpOHuHgk6Mqg l0tcpGbvwVSAoNoHuMY0 =WQd6 -----END PGP SIGNATURE----- --T4sUOijqQbZv57TR-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/