From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90C05206071 for ; Tue, 29 Oct 2024 13:20:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730208048; cv=none; b=hJlg2H47KvsHqcTbuB/6lzuO1zdtOwXHmznCuIlf9S/Yd5v7WcuXsxa6ADbi3OWh8ZKYHazKs4//Ml17DkY9RDRr1hZQVi5tkeSjwgyvMkMSdONYanzfbzeDG5V/FBeeE089WUZIs4AhNAjvL9wZTJZNCxZuC76JBGuxWZpGae4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730208048; c=relaxed/simple; bh=atIdjrSoz8cQOo8Oh3x41BjnGBTqmvpWtHpYQOqBTIY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=SEKyFMpXsJQBF5v+/IBNYYPM5tJkcOkLe0xYjtoG/hIo9ANjm7RxPnPEGqMUtkL/twaRzWd9oz0p23455l/4wTkENpif7tOqx32jwfryXfp6/0tZhJa+vwr67Jj6pQcYoMlTN0pAnvGteb49WUft99sWcW7AhqLp6mMjoxAqbrg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=maPSauNb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="maPSauNb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC2F1C4CECD; Tue, 29 Oct 2024 13:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730208048; bh=atIdjrSoz8cQOo8Oh3x41BjnGBTqmvpWtHpYQOqBTIY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=maPSauNb/CNnnievFOAFYOU7f38+08j7hlhokWmUHB9io3DNtx2BMgx4rZ0txddjB GO8ZTV8Myxrx2wOfS6tluq1+dap7q3kdp9o7AzxslPu8PzWJnGuO7vErF09+/TEoo1 XM23aIbOHbl66pxZKZGD46phpT/55IPOE5AbfNddUd7sWMd1Vf13R04tg2TjkwE9Yb X9nAvwaG0+niGCVERR8HS2UT9TMxZQLIL9oBm0k6cn4oKl8R0xerfhbm1u5/XPgjM2 yAhn/JrOghfLEPizGb6UQ28HL7Ssbje5uHGypz186z62YAeTi3zJocUTxeNxv8zoXe Gah5N6nGQt5jg== Date: Tue, 29 Oct 2024 13:20:43 +0000 From: Will Deacon To: huanglei Cc: catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, huanglei , arnd@arndb.de Subject: Re: Re: [PATCH] arm64/Kconfig: introduce GENERIC_ISA_DMA Message-ID: <20241029132042.GA4416@willie-the-truck> References: <20241025011641.4858-1-huanglei814@163.com> <20241028150544.GA2445@willie-the-truck> <26ed8fbb.1809.192d5ef13e5.Coremail.huanglei814@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <26ed8fbb.1809.192d5ef13e5.Coremail.huanglei814@163.com> User-Agent: Mutt/1.10.1 (2018-07-13) On Tue, Oct 29, 2024 at 09:41:08AM +0800, huanglei wrote: > Even if MAX_SMA_CANNELS is not defined, as long as GENETIC-SIA_DMA is > enabled， request_rma/free_rma function will also be exported, and > other modules using these two interfaces will not encounter link > errors. > > I don't know why others haven't noticed, but I discovered it when > debugging pcie parallel port drivers. And the arm/Kconfig has been > around for a long time. Please try to avoid top-posting in replies, as it makes the conversation very hard to follow. > At 2024-10-28 22:05:45, "Will Deacon" wrote: > >On Fri, Oct 25, 2024 at 09:16:41AM +0800, huanglei814 wrote: > >> From: huanglei > >> > >> Enable GENERIC_ISA_DMA feature on arm64 platform, > >> thus, request_dma and free_dma interface can be export. > >> and driver modules can use the this interfaces on arm64 > >> platform. > >> > >> Currently, many pcie parallel port drivers still use these > >> interfaces when ported to arm64 platform. > > > >Why has it taken so long for anybody to notice? > > > >> Signed-off-by: huanglei > >> --- > >> arch/arm64/Kconfig | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > >> index fd9df6dcc593..986eb251f68f 100644 > >> --- a/arch/arm64/Kconfig > >> +++ b/arch/arm64/Kconfig > >> @@ -367,6 +367,9 @@ config GENERIC_CSUM > >> config GENERIC_CALIBRATE_DELAY > >> def_bool y > >> > >> +config GENERIC_ISA_DMA > >> + def_bool y > >> + > > > > Does this actually do anything without MAX_DMA_CHANNELS defined? > > Even if MAX_SMA_CANNELS is not defined, as long as GENETIC-SIA_DMA is > enabled， request_rma/free_rma function will also be exported, and > other modules using these two interfaces will not encounter link > errors. Do the drivers do anything useful after they've linked? Can you please provide some in-tree examples of drivers that can be used on arm64 only once GENERIC_ISA_DMA is selected? If they just need some stubs for request_dma() and free_dma(), then it feels to me like that should be the default implementation, rather than having to select something to get them. Will