From mboxrd@z Thu Jan 1 00:00:00 1970 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 4166EC433FE for ; Mon, 3 Jan 2022 16:15:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234411AbiACQPU (ORCPT ); Mon, 3 Jan 2022 11:15:20 -0500 Received: from netrider.rowland.org ([192.131.102.5]:49835 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S233621AbiACQPR (ORCPT ); Mon, 3 Jan 2022 11:15:17 -0500 Received: (qmail 1188656 invoked by uid 1000); 3 Jan 2022 11:15:16 -0500 Date: Mon, 3 Jan 2022 11:15:16 -0500 From: Alan Stern To: Niklas Schnelle Cc: Arnd Bergmann , Bjorn Helgaas , John Garry , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Greg Kroah-Hartman , Mathias Nyman , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pci@vger.kernel.org, linux-riscv@lists.infradead.org, linux-csky@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [RFC 31/32] usb: handle HAS_IOPORT dependencies Message-ID: References: <20211227164317.4146918-1-schnelle@linux.ibm.com> <20211227164317.4146918-32-schnelle@linux.ibm.com> <8bda347ea30b60f1edb55693ff7509e7f7b1f979.camel@linux.ibm.com> <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 03, 2022 at 12:35:45PM +0100, Niklas Schnelle wrote: > On Fri, 2021-12-31 at 12:15 -0500, Alan Stern wrote: > > On Fri, Dec 31, 2021 at 12:06:24PM +0100, Niklas Schnelle wrote: > > > On Mon, 2021-12-27 at 15:36 -0500, Alan Stern wrote: > > > > On Mon, Dec 27, 2021 at 05:43:16PM +0100, Niklas Schnelle wrote: > > > > > diff --git a/drivers/usb/host/uhci-hcd.h b/drivers/usb/host/uhci-hcd.h > > > > > index 8ae5ccd26753..8e30116b6fd2 100644 > > > > > --- a/drivers/usb/host/uhci-hcd.h > > > > > +++ b/drivers/usb/host/uhci-hcd.h > > > > > @@ -586,12 +586,14 @@ static inline int uhci_aspeed_reg(unsigned int reg) > > > > > > > > > > static inline u32 uhci_readl(const struct uhci_hcd *uhci, int reg) > > > > > { > > > > > +#ifdef CONFIG_HAS_IOPORT > > > > > if (uhci_has_pci_registers(uhci)) > > > > > return inl(uhci->io_addr + reg); > > > > > - else if (uhci_is_aspeed(uhci)) > > > > > +#endif > > > > > > > > Instead of making all these changes (here and in the hunks below), you > > > > can simply modify the definition of uhci_has_pci_registers() so that it > > > > always gives 0 when CONFIG_HAS_IOPORT is N. > > > > > > > > Alan Stern > > > > > > I don't think that works, for example in the hunk you quoted returning > > > 0 from uhci_has_pci_registers() only skips over the inl() at run-time. > > > We're aiming to have inl() undeclared if HAS_IOPORT is unset though. > > > > I see. Do you think the following would be acceptable? Add: > > > > #ifdef CONFIG_HAS_IOPORT > > #define UHCI_IN(x) x > > #define UHCI_OUT(x) x > > #else > > #define UHCI_IN(x) 0 > > #define UHCI_OUT(x) > > #endif > > > > and then replace for example inl(uhci->io_addr + reg) with > > UHCI_IN(inl(uhci->io_addr + reg)). > > In principle that looks like a valid approach. Not sure this is better > than explicit ifdefs though. The general preference in the kernel is to avoid sprinkling #ifdef's throughout function definitions, and instead encapsulate their effects with macros or inline functions -- like this. > With this approach one could add > UHCI_IN()/UHCI_OUT() calls which end up as nops without realizing it as > it would disable any compile time warning for using them without > guarding against CONFIG_HAS_IOPORT being undefined. To help prevent that, we can add #undef UHCI_IN #undef UHCI_OUT at the end of this section. > > The definition of uhci_has_pci_registers() should be updated in any > > case; there's no reason for it to do a runtime check of uhci->io_addr > > when HAS_IOPORT is disabled. > > Agree. Interestingly same as with the "if > (IS_ENABLED(CONFIG_HAS_IOPORT))" it seems having > uhci_has_pci_registers() compile-time defined to 0 (I added a > defined(CONFIG_HAS_IOPORT) to it) makes the compiler ignore the missing > inl() decleration already. But I'm not sure if we should rely on that. I definitely would not rely on it. Alan Stern From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D9F8CC433EF for ; Mon, 3 Jan 2022 16:15:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Jziuow9j+u4yKWpMgvmjUls/78KA3a2i824N/kYNKOY=; b=C6WsOS+P7JxhWD HfjaA2LdaAIkXEv1PhSXjYIxuF/fK1A2vIfZXtrG/E40c1pCZ9aYB+lVkPui/vpvFztqYJLRKRcsF I7n0T80AtT0ukK0BOlN557xx3BgWLzvkDoIh3SVqBYj7QLYnJmQMo/r/LUK8NR9RsvcNmp0ejjDOh RitBJLfMfgXibwER5B9emP+TzMCwXdbodlT4TA3UwkrfVqFsnX8kzaWTbvfvwhEh+YHON9moVKYEX +tpXx2tW0H1NFIXb5kl4kYHv9mFjIH19RmKPd/NT7Yva2Z3G/IJvBfr+xyACUF0cyL6jMe6JIF94j yO9MwfxqfVULZgeiWbKQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n4Pza-009RVU-AU; Mon, 03 Jan 2022 16:15:26 +0000 Received: from netrider.rowland.org ([192.131.102.5]) by bombadil.infradead.org with smtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n4PzW-009RUG-Md for linux-riscv@lists.infradead.org; Mon, 03 Jan 2022 16:15:24 +0000 Received: (qmail 1188656 invoked by uid 1000); 3 Jan 2022 11:15:16 -0500 Date: Mon, 3 Jan 2022 11:15:16 -0500 From: Alan Stern To: Niklas Schnelle Cc: Arnd Bergmann , Bjorn Helgaas , John Garry , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Greg Kroah-Hartman , Mathias Nyman , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pci@vger.kernel.org, linux-riscv@lists.infradead.org, linux-csky@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [RFC 31/32] usb: handle HAS_IOPORT dependencies Message-ID: References: <20211227164317.4146918-1-schnelle@linux.ibm.com> <20211227164317.4146918-32-schnelle@linux.ibm.com> <8bda347ea30b60f1edb55693ff7509e7f7b1f979.camel@linux.ibm.com> <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220103_081522_933604_41EB6459 X-CRM114-Status: GOOD ( 28.35 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Jan 03, 2022 at 12:35:45PM +0100, Niklas Schnelle wrote: > On Fri, 2021-12-31 at 12:15 -0500, Alan Stern wrote: > > On Fri, Dec 31, 2021 at 12:06:24PM +0100, Niklas Schnelle wrote: > > > On Mon, 2021-12-27 at 15:36 -0500, Alan Stern wrote: > > > > On Mon, Dec 27, 2021 at 05:43:16PM +0100, Niklas Schnelle wrote: > > > > > diff --git a/drivers/usb/host/uhci-hcd.h b/drivers/usb/host/uhci-hcd.h > > > > > index 8ae5ccd26753..8e30116b6fd2 100644 > > > > > --- a/drivers/usb/host/uhci-hcd.h > > > > > +++ b/drivers/usb/host/uhci-hcd.h > > > > > @@ -586,12 +586,14 @@ static inline int uhci_aspeed_reg(unsigned int reg) > > > > > > > > > > static inline u32 uhci_readl(const struct uhci_hcd *uhci, int reg) > > > > > { > > > > > +#ifdef CONFIG_HAS_IOPORT > > > > > if (uhci_has_pci_registers(uhci)) > > > > > return inl(uhci->io_addr + reg); > > > > > - else if (uhci_is_aspeed(uhci)) > > > > > +#endif > > > > > > > > Instead of making all these changes (here and in the hunks below), you > > > > can simply modify the definition of uhci_has_pci_registers() so that it > > > > always gives 0 when CONFIG_HAS_IOPORT is N. > > > > > > > > Alan Stern > > > > > > I don't think that works, for example in the hunk you quoted returning > > > 0 from uhci_has_pci_registers() only skips over the inl() at run-time. > > > We're aiming to have inl() undeclared if HAS_IOPORT is unset though. > > > > I see. Do you think the following would be acceptable? Add: > > > > #ifdef CONFIG_HAS_IOPORT > > #define UHCI_IN(x) x > > #define UHCI_OUT(x) x > > #else > > #define UHCI_IN(x) 0 > > #define UHCI_OUT(x) > > #endif > > > > and then replace for example inl(uhci->io_addr + reg) with > > UHCI_IN(inl(uhci->io_addr + reg)). > > In principle that looks like a valid approach. Not sure this is better > than explicit ifdefs though. The general preference in the kernel is to avoid sprinkling #ifdef's throughout function definitions, and instead encapsulate their effects with macros or inline functions -- like this. > With this approach one could add > UHCI_IN()/UHCI_OUT() calls which end up as nops without realizing it as > it would disable any compile time warning for using them without > guarding against CONFIG_HAS_IOPORT being undefined. To help prevent that, we can add #undef UHCI_IN #undef UHCI_OUT at the end of this section. > > The definition of uhci_has_pci_registers() should be updated in any > > case; there's no reason for it to do a runtime check of uhci->io_addr > > when HAS_IOPORT is disabled. > > Agree. Interestingly same as with the "if > (IS_ENABLED(CONFIG_HAS_IOPORT))" it seems having > uhci_has_pci_registers() compile-time defined to 0 (I added a > defined(CONFIG_HAS_IOPORT) to it) makes the compiler ignore the missing > inl() decleration already. But I'm not sure if we should rely on that. I definitely would not rely on it. Alan Stern _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv