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 F26F51714C8; Sat, 24 Aug 2024 05:18:38 +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=1724476719; cv=none; b=N09GlILQ8gTUQeW0JrIIaNfOF0jNot+Ka7bW8g1BAbJNLj8B9qMfrnRNj9O19P4L1IecpwhEwUZLHBSqC6N6up2zqocDOqnYko5e9cy/KKYeJ0867aFUpD1YHg35apz7vJ/3tzqIAvT/0cfgbGzUE7OjUZ+fiI4CXKnN8hK4qeQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724476719; c=relaxed/simple; bh=A86GmKBdFIJ2osp8JS9casQOmwY8tO+gEpbE1F7UnWY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=htRF0tfyi5yNLEGwmsoyZOFucrvWso8lXy0l7ezdBmFXR/MVZaIngxRiCEpF6v/H3jRLIkaJg2XjjSqmS6u3k7Hi/N0cu/ppm6c7+H4i1pPETXr8+IvsYkqJ9gLznsOFVWTHJMYfcv50akC//JkAUz0zy3nMwbjHTLyNkgWPSp4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SXEbpwpH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SXEbpwpH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33C53C32781; Sat, 24 Aug 2024 05:18:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1724476718; bh=A86GmKBdFIJ2osp8JS9casQOmwY8tO+gEpbE1F7UnWY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SXEbpwpHLF1UnDvKOEGQVJmfbA6FgOzdqnyQD8cbH546wQ+Bg1O3yLjnsbBsWqJrg vnV8Ws/g2/z++BD11JKoyz2gnWhq6mi9TkLL+KW+vhGiLGswE3AEsIK23yG9fsDkka eHQqu2uz18SGiKQhVxTIFwuMCDTh+Xx5Q6sOrM0g= Date: Sat, 24 Aug 2024 11:29:10 +0800 From: Greg Kroah-Hartman To: Ira Weiny Cc: Zijun Hu , "Rafael J. Wysocki" , Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Dan Williams , Takashi Sakamoto , Timur Tabi , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, linux1394-devel@lists.sourceforge.net, netdev@vger.kernel.org, Zijun Hu Subject: Re: [PATCH v2 2/4] cxl/region: Prevent device_find_child() from modifying caller's match data Message-ID: <2024082420-vantage-thesaurus-99f2@gregkh> References: <20240815-const_dfc_prepare-v2-0-8316b87b8ff9@quicinc.com> <20240815-const_dfc_prepare-v2-2-8316b87b8ff9@quicinc.com> <66c4a136d9764_2ddc2429435@iweiny-mobl.notmuch> 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=us-ascii Content-Disposition: inline In-Reply-To: <66c4a136d9764_2ddc2429435@iweiny-mobl.notmuch> On Tue, Aug 20, 2024 at 08:59:18AM -0500, Ira Weiny wrote: > Zijun Hu wrote: > > From: Zijun Hu > > > > To prepare for constifying the following old driver core API: > > > > struct device *device_find_child(struct device *dev, void *data, > > int (*match)(struct device *dev, void *data)); > > to new: > > struct device *device_find_child(struct device *dev, const void *data, > > int (*match)(struct device *dev, const void *data)); > > > > The new API does not allow its match function (*match)() to modify > > caller's match data @*data, but match_free_decoder() as the old API's > > match function indeed modifies relevant match data, so it is not > > suitable for the new API any more, fixed by implementing a equivalent > > cxl_device_find_child() instead of the old API usage. > > Generally it seems ok but I think some name changes will make this more > clear. See below. > > Also for those working on CXL I'm questioning the use of ID here and the > dependence on the id's being added to the parent in order. Is that a > guarantee? > > > > > Signed-off-by: Zijun Hu > > --- > > drivers/cxl/core/region.c | 36 +++++++++++++++++++++++++++++++++++- > > 1 file changed, 35 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > > index 21ad5f242875..8d8f0637f7ac 100644 > > --- a/drivers/cxl/core/region.c > > +++ b/drivers/cxl/core/region.c > > @@ -134,6 +134,39 @@ static const struct attribute_group *get_cxl_region_access1_group(void) > > return &cxl_region_access1_coordinate_group; > > } > > > > +struct cxl_dfc_data { > > struct cxld_match_data > > 'cxld' == cxl decoder in our world. > > > + int (*match)(struct device *dev, void *data); > > + void *data; > > + struct device *target_device; > > +}; > > + > > +static int cxl_dfc_match_modify(struct device *dev, void *data) > > Why not just put this logic into match_free_decoder? > > > +{ > > + struct cxl_dfc_data *dfc_data = data; > > + int res; > > + > > + res = dfc_data->match(dev, dfc_data->data); > > + if (res && get_device(dev)) { > > + dfc_data->target_device = dev; > > + return res; > > + } > > + > > + return 0; > > +} > > + > > +/* > > + * I have the same function as device_find_child() but allow to modify > > + * caller's match data @*data. > > + */ > > No need for this comment after the new API is established. > > > +static struct device *cxl_device_find_child(struct device *parent, void *data, > > + int (*match)(struct device *dev, void *data)) > > +{ > > + struct cxl_dfc_data dfc_data = {match, data, NULL}; > > + > > + device_for_each_child(parent, &dfc_data, cxl_dfc_match_modify); > > + return dfc_data.target_device; > > +} > > + > > static ssize_t uuid_show(struct device *dev, struct device_attribute *attr, > > char *buf) > > { > > @@ -849,7 +882,8 @@ cxl_region_find_decoder(struct cxl_port *port, > > dev = device_find_child(&port->dev, &cxlr->params, > > match_auto_decoder); > > else > > - dev = device_find_child(&port->dev, &id, match_free_decoder); > > + dev = cxl_device_find_child(&port->dev, &id, > > + match_free_decoder); > > This is too literal. How about the following (passes basic cxl-tests). > > Ira > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index 21ad5f242875..c1e46254efb8 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -794,10 +794,15 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos) > return rc; > } > > +struct cxld_match_data { > + int id; > + struct device *target_device; > +}; > + > static int match_free_decoder(struct device *dev, void *data) > { > + struct cxld_match_data *match_data = data; > struct cxl_decoder *cxld; > - int *id = data; > > if (!is_switch_decoder(dev)) > return 0; > @@ -805,17 +810,30 @@ static int match_free_decoder(struct device *dev, void *data) > cxld = to_cxl_decoder(dev); > > /* enforce ordered allocation */ > - if (cxld->id != *id) > + if (cxld->id != match_data->id) > return 0; > > - if (!cxld->region) > + if (!cxld->region && get_device(dev)) { > + match_data->target_device = dev; > return 1; > + } > > - (*id)++; > + match_data->id++; > > return 0; > } > > +static struct device *find_free_decoder(struct device *parent) > +{ > + struct cxld_match_data match_data = { > + .id = 0, > + .target_device = NULL, > + }; > + > + device_for_each_child(parent, &match_data, match_free_decoder); > + return match_data.target_device; > +} I like this type of re-write much better, thanks! greg k-h