Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752913AbbF1TrL (ORCPT ); Sun, 28 Jun 2015 15:47:11 -0400 Received: from mail-wi0-f173.google.com ([209.85.212.173]:38733 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752671AbbF1Tqv (ORCPT ); Sun, 28 Jun 2015 15:46:51 -0400 From: Marek Belisko To: jslaby@suse.cz, gregkh@linuxfoundation.org, arnd@arndb.de Cc: peter@hurleysoftware.com, mark.rutland@arm.com, gnomes@lxorguk.ukuu.org.uk, sre@kernel.org, neil@brown.name, grant.likely@linaro.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, robh+dt@kernel.org, pawel.moll@arm.com, hns@goldelico.com, Marek Belisko Subject: [PATCH RFC v2 1/3] tty: serial core: provide method to search uart by phandle Date: Sun, 28 Jun 2015 21:46:24 +0200 Message-Id: <1435520786-31867-2-git-send-email-marek@goldelico.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1435520786-31867-1-git-send-email-marek@goldelico.com> References: <1435520786-31867-1-git-send-email-marek@goldelico.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7666 Lines: 226 From: "H. Nikolaus Schaller" 1. add registered uart_ports to a search list 2. provide a function to search an uart_port by phandle. This copies the mechanism how devm_usb_get_phy_by_phandle() works Signed-off-by: H. Nikolaus Schaller Signed-off-by: Marek Belisko --- Documentation/serial/slaves.txt | 36 ++++++++++++++ drivers/tty/serial/serial_core.c | 103 +++++++++++++++++++++++++++++++++++++++ include/linux/serial_core.h | 10 ++++ 3 files changed, 149 insertions(+) create mode 100644 Documentation/serial/slaves.txt diff --git a/Documentation/serial/slaves.txt b/Documentation/serial/slaves.txt new file mode 100644 index 0000000..6f8d44d --- /dev/null +++ b/Documentation/serial/slaves.txt @@ -0,0 +1,36 @@ +UART slave device support + +A remote device connected to a RS232 interface is usually power controlled by the DTR line. +The DTR line is managed automatically by the UART driver for open() and close() syscalls +and on demand by tcsetattr(). + +With embedded devices, the serial peripheral might be directly and always connected to the UART +and there might be no physical DTR line involved. Power control (on/off) has to be done by some +chip specific device driver (which we call "UART slave") through some mechanisms (I2C, GPIOs etc.) +not related to the serial interface. Some devices do not explicitly tell their power state except +by sending or not sending data to the UART. In such a case the device driver must be able to monitor +data activity. The role of the device driver is to encapsulate such power control in a single place. + +This patch series allows to support such drivers by providing: +* a mechanism that a slave driver can identify the UART instance it is connected to +* a mechanism that UART slave drivers can register to be notified +* notfications for DTR (and other modem control) state changes +* notifications that the UART has received some data from the UART + +A slave device simply adds a phandle reference to the UART it is connected to, e.g. + + gps { + compatible = "wi2wi,w2sg0004"; + uart = <&uart1>; + }; + +The slave driver calls devm_serial_get_uart_by_phandle() to identify the uart driver. +This API follows the concept of devm_usb_get_phy_by_phandle(). + +A slave device driver registers itself with serial_register_slave() to receive notifications. +Notification handler callbacks can be registered by serial_register_mctrl_notification() and +serial_register_rx_notification(). If an UART has registered a NULL slave or a NULL handler, +no notifications are sent. + +RX notification handlers can define a ktermios during setup and the handler function can modify +or decide to throw away each character that is passed upwards. diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index eec067d..ad61441 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -38,6 +38,33 @@ #include #include +static LIST_HEAD(uart_list); +static DEFINE_SPINLOCK(uart_lock); + +/* same concept as __of_usb_find_phy */ +static struct uart_port *__of_serial_find_uart(struct device_node *node) +{ + struct uart_port *uart; + + if (!of_device_is_available(node)) + return ERR_PTR(-ENODEV); + + list_for_each_entry(uart, &uart_list, head) { + if (node != uart->dev->of_node) + continue; + + return uart; + } + + return ERR_PTR(-EPROBE_DEFER); +} + +static void devm_serial_uart_release(struct device *dev, void *res) +{ + struct uart_port *uart = *(struct uart_port **)res; + /* FIXME: serial_put_uart(uart); */ +} + /* * This is used to lock changes in serial line configuration. */ @@ -64,6 +91,78 @@ static int uart_dcd_enabled(struct uart_port *uport) return !!(uport->status & UPSTAT_DCD_ENABLE); } +/** + * devm_serial_get_uart_by_phandle - find the uart by phandle + * @dev - device that requests this uart + * @phandle - name of the property holding the uart phandle value + * @index - the index of the uart + * + * Returns the uart_port associated with the given phandle value, + * after getting a refcount to it, -ENODEV if there is no such uart or + * -EPROBE_DEFER if there is a phandle to the uart, but the device is + * not yet loaded. While at that, it also associates the device with + * the uart using devres. On driver detach, release function is invoked + * on the devres data, then, devres data is freed. + * + * For use by tty host and peripheral drivers. + */ + +/* same concept as devm_usb_get_phy_by_phandle() */ + +struct uart_port *devm_serial_get_uart_by_phandle(struct device *dev, + const char *phandle, u8 index) +{ + struct uart_port *uart = ERR_PTR(-ENOMEM), **ptr; + unsigned long flags; + struct device_node *node; + + if (!dev->of_node) { + dev_err(dev, "device does not have a device node entry\n"); + return ERR_PTR(-EINVAL); + } + + node = of_parse_phandle(dev->of_node, phandle, index); + if (!node) { + dev_err(dev, "failed to get %s phandle in %s node\n", phandle, + dev->of_node->full_name); + return ERR_PTR(-ENODEV); + } + + ptr = devres_alloc(devm_serial_uart_release, sizeof(*ptr), GFP_KERNEL); + if (!ptr) { + dev_err(dev, "failed to allocate memory for devres\n"); + goto err0; + } + + spin_lock_irqsave(&uart_lock, flags); + + uart = __of_serial_find_uart(node); + if (IS_ERR(uart)) { + devres_free(ptr); + goto err1; + } + + if (!try_module_get(uart->dev->driver->owner)) { + uart = ERR_PTR(-ENODEV); + devres_free(ptr); + goto err1; + } + + *ptr = uart; + devres_add(dev, ptr); + + get_device(uart->dev); + +err1: + spin_unlock_irqrestore(&uart_lock, flags); + +err0: + of_node_put(node); + + return uart; +} +EXPORT_SYMBOL_GPL(devm_serial_get_uart_by_phandle); + /* * This routine is used by the interrupt handler to schedule processing in * the software interrupt portion of the driver. @@ -2727,6 +2826,8 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport) */ uport->flags &= ~UPF_DEAD; + list_add_tail(&uport->head, &uart_list); + out: mutex_unlock(&port->mutex); mutex_unlock(&port_mutex); @@ -2758,6 +2859,8 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport) mutex_lock(&port_mutex); + list_del(&uport->head); + /* * Mark the port "dead" - this prevents any opens from * succeeding while we shut down the port. diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 297d4fa..ba23718 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -247,6 +247,7 @@ struct uart_port { const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ struct serial_rs485 rs485; void *private_data; /* generic platform data pointer */ + struct list_head head; /* list of uarts e.g. to look up by phandle */ }; static inline int serial_port_in(struct uart_port *up, int offset) @@ -475,4 +476,13 @@ static inline int uart_handle_break(struct uart_port *port) (cflag) & CRTSCTS || \ !((cflag) & CLOCAL)) +/* + * Helper functions for UART slave drivers + */ + +/* find UART by phandle (e.g. with 'uart = <&uart2>;' then call as + * devm_serial_get_uart_by_phandle(dev, "uart", 0); + */ +extern struct uart_port *devm_serial_get_uart_by_phandle(struct device *dev, + const char *phandle, u8 index); #endif /* LINUX_SERIAL_CORE_H */ -- 1.9.1 -- 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/