From nobody Tue Apr 7 00:43:19 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E800ECAAD3 for ; Thu, 1 Sep 2022 11:07:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233589AbiIALHQ (ORCPT ); Thu, 1 Sep 2022 07:07:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233671AbiIALHI (ORCPT ); Thu, 1 Sep 2022 07:07:08 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D9211321E8; Thu, 1 Sep 2022 04:07:07 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 28A8822685; Thu, 1 Sep 2022 11:07:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1662030426; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6xhXqxiB9OvJti0BiVcQUaA8ec/RM1KadmGL+YamEp0=; b=xbl28LfvEIg5H4LJOcwRZ94mlhm986g2KcWJtnrFZCZAWRRogJcotTjLWDGWEswGvZLp4f gg8qQnemXaCWlgcPlCBejqnuQSoosG2WlBtzuViGAbSmISdimhuq3Ku3PiCM9GDiJpGHEg 8A2ocox/2UsYMRC7oETLvtCDUsp/9yY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1662030426; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6xhXqxiB9OvJti0BiVcQUaA8ec/RM1KadmGL+YamEp0=; b=CXnNMDABF6QeBz1OE5PrvppS4p8DZ1EhnC72taOC7LzvwS4MB+IM39IyyHcAuZ39ivhhC6 vwzZJ4kDmV8UUwCg== Received: from localhost.localdomain (unknown [10.100.208.98]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id ABC1F2C142; Thu, 1 Sep 2022 11:07:05 +0000 (UTC) From: Jiri Slaby To: gregkh@linuxfoundation.org Cc: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Jiri Slaby Subject: [PATCH v2 1/3] tty: serial: introduce transmit helper generators Date: Thu, 1 Sep 2022 13:06:55 +0200 Message-Id: <20220901110657.3305-2-jslaby@suse.cz> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220901110657.3305-1-jslaby@suse.cz> References: <20220901110657.3305-1-jslaby@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Many serial drivers do the same thing: * send x_char if set * keep sending from the xmit circular buffer until either - the loop reaches the end of the xmit buffer - TX is stopped - HW fifo is full * check for pending characters and: - wake up tty writers to fill for more data into xmit buffer - stop TX if there is nothing in the xmit buffer The only differences are: * how to write the character to the HW fifo * the check of the end condition: - is the HW fifo full? - is limit of the written characters reached? So unify the above into two helper generators: * DEFINE_UART_PORT_TX_HELPER_LIMITED() -- it performs the above taking the written characters limit into account, and * DEFINE_UART_PORT_TX_HELPER() -- the same as above, except it only checks the HW readiness, not the characters limit. The HW specific operations (as stated as "differences" above) are passed as arguments to the macros. They are: * tx_ready() -- returns true if HW can accept more data. * put_char() -- write a character to the device. * tx_done() -- when the write loop is done, perform arbitrary action before potential invocation of ops->stop_tx() happens. Note that the above macros are generators. This means the code is generated in place and the above 3 arguments are "inlined". I.e. no added penalty by generating call instructions for every single character. Nor any indirect calls. (As in previous versions of this patchset.) Signed-off-by: Jiri Slaby --- Notes: [v2] instead of a function (uart_port_tx_limit()) in serial_core, generate these in-place using macros. Thus eliminating "call" penalty. Documentation/driver-api/serial/driver.rst | 3 + include/linux/serial_core.h | 86 ++++++++++++++++++++++ 2 files changed, 89 insertions(+) diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/dri= ver-api/serial/driver.rst index 23c6b956cd90..25775bf1fcc6 100644 --- a/Documentation/driver-api/serial/driver.rst +++ b/Documentation/driver-api/serial/driver.rst @@ -78,6 +78,9 @@ Other functions uart_get_lsr_info uart_handle_dcd_change uart_handle_cts_change uart_try_toggle_sysrq uart_get_console =20 +.. kernel-doc:: include/linux/serial_core.h + :identifiers: DEFINE_UART_PORT_TX_HELPER_LIMITED DEFINE_UART_PORT_TX_HE= LPER + Other notes ----------- =20 diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 6e4f4765d209..715778160ae1 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -646,6 +646,92 @@ struct uart_driver { =20 void uart_write_wakeup(struct uart_port *port); =20 +#define __DEFINE_UART_PORT_TX_HELPER(name, port, ch, tx_ready, put_char, \ + tx_done, for_test, for_post, ...) \ +unsigned int name(struct uart_port *port __VA_OPT__(,) __VA_ARGS__) \ +{ \ + struct circ_buf *xmit =3D &port->state->xmit; \ + unsigned int pending; \ + u8 ch; \ + \ + for (; (for_test) && (tx_ready); (for_post), port->icount.tx++) { \ + if (port->x_char) { \ + ch =3D port->x_char; \ + (put_char); \ + port->x_char =3D 0; \ + continue; \ + } \ + \ + if (uart_circ_empty(xmit) || uart_tx_stopped(port)) \ + break; \ + \ + ch =3D xmit->buf[xmit->tail]; \ + (put_char); \ + xmit->tail =3D (xmit->tail + 1) % UART_XMIT_SIZE; \ + } \ + \ + (tx_done); \ + \ + pending =3D uart_circ_chars_pending(xmit); \ + if (pending < WAKEUP_CHARS) { \ + uart_write_wakeup(port); \ + \ + if (pending =3D=3D 0) \ + port->ops->stop_tx(port); \ + } \ + \ + return pending; \ +} + +/** + * DEFINE_UART_PORT_TX_HELPER_LIMITED -- generate transmit helper for uart= _port + * with count limiting + * @name: name of the helper to generate + * @port: name of variable holding uart_port + * @ch: name of variable holding a character to write + * @tx_ready: can HW accept more data function + * @put_char: function to write a character + * @tx_done: function to call after the loop is done + * + * This macro generates a function @name. The generated function is meant = as a + * helper to transmit characters from the xmit buffer to the hardware using + * @put_char(). It does so until count (passed to @name) characters are se= nt + * and while @tx_ready() still returns non-zero (if non-NULL). + * + * The generated function returns the number of characters in the xmit buf= fer + * when done. + * + * The functions in parameters shall be designed as follows: + * * **tx_ready(port):** the function shall return true if the HW can acc= ept + * more data to be sent. This function can be %NULL, which means the HW= is + * always ready. + * * **put_char(port, ch):** the function shall write @ch to the device. + * * **tx_done(port):** when the write loop is done, this function can + * perform arbitrary action before potential invocation of ops->stop_tx= () + * happens. This function can be %NULL. + * + * For all of them, @port->lock is held, interrupts are locally disabled a= nd + * the functions must not sleep. + */ +#define DEFINE_UART_PORT_TX_HELPER_LIMITED(name, port, ch, tx_ready, put_c= har, \ + tx_done) \ + __DEFINE_UART_PORT_TX_HELPER(name, port, ch, tx_ready, put_char, \ + tx_done, count, count--, unsigned int count) + +/** + * DEFINE_UART_PORT_TX_HELPER -- generate transmit helper for uart_port + * @name: name of the helper to generate + * @port: name of variable holding uart_port + * @ch: name of variable holding a character to write + * @tx_ready: can HW accept more data function + * @put_char: function to write a character + * + * See DEFINE_UART_PORT_TX_HELPER_LIMITED() for more details. + */ +#define DEFINE_UART_PORT_TX_HELPER(name, port, ch, tx_ready, put_char) \ + __DEFINE_UART_PORT_TX_HELPER(name, port, ch, tx_ready, put_char, \ + ({}), true, ({})) + /* * Baud rate helpers. */ --=20 2.37.2