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Message-ID: <alpine.DEB.2.22.394.2212311237320.2138420@rhweight-WRK1> Date: Sat, 31 Dec 2022 12:46:28 -0800 (PST) From: matthew.gerlach@...ux.intel.com To: Xu Yilun <yilun.xu@...el.com> cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, hao.wu@...el.com, russell.h.weight@...el.com, basheer.ahmed.muddebihal@...el.com, trix@...hat.com, mdf@...nel.org, linux-fpga@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, tianfei.zhang@...el.com, corbet@....net, gregkh@...uxfoundation.org, linux-serial@...r.kernel.org, jirislaby@...nel.org, geert+renesas@...der.be, niklas.soderlund+renesas@...natech.se, macro@...am.me.uk, johan@...nel.org, lukas@...ner.de, ilpo.jarvinen@...ux.intel.com, marpagan@...hat.com, bagasdotme@...il.com Subject: Re: [PATCH v7 3/4] fpga: dfl: add basic support for DFHv1 On Mon, 26 Dec 2022, Xu Yilun wrote: > On 2022-12-21 at 11:14:59 -0800, matthew.gerlach@...ux.intel.com wrote: >> >> >> On Tue, 20 Dec 2022, Andy Shevchenko wrote: >> >>> On Tue, Dec 20, 2022 at 08:36:51AM -0800, matthew.gerlach@...ux.intel.com wrote: >>>> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com> >>>> >>>> Version 1 of the Device Feature Header (DFH) definition adds >>>> functionality to the DFL bus. >>>> >>>> A DFHv1 header may have one or more parameter blocks that >>>> further describes the HW to SW. Add support to the DFL bus >>>> to parse the MSI-X parameter. >>>> >>>> The location of a feature's register set is explicitly >>>> described in DFHv1 and can be relative to the base of the DFHv1 >>>> or an absolute address. Parse the location and pass the information >>>> to DFL driver. >>> >>> ... >>> >>>> +/** >>>> + * dfh_find_param() - find data for the given parameter id >>>> + * @dfl_dev: dfl device >>>> + * @param: id of dfl parameter >>>> + * >>>> + * Return: pointer to parameter header on success, NULL otherwise. >>> >>> header is a bit confusing here, does it mean we give and ID and we got >>> something more than just a data as summary above suggests? >> >> Yes, the summary is not correct. It should say "find the parameter block >> for the given parameter id". >> >>> >>> In such case summary and this text should clarify what exactly we get >>> and layout of the data. Since this is a pointer, who is responsible of >>> checking out-of-boundary accesses? For instance, if the parameters are >>> variadic by length the length should be returned as well. Otherwise it >>> should be specified as a constant somewhere, right? >> >> The parameter header has the next/size field; so the caller of >> dfh_find_param should perform boundary checking as part of interpreting the >> parameter data. I think a function to perform this checking and data >> interpretation would help here. > > It is better the DFL core provides the size of the parameter block, just > in this API. It provides the pointer and should be ensured the memory > for the pointer be correctly understood. Ok, how about the following API for dfh_find_param? /** * dfh_find_param() - find parameter block for the given parameter id * @dfl_dev: dfl device * @param_id: id of dfl parameter * @pver: destination to store parameter version * @pcount: destination to store size of parameter data in u64 bit words * * Return: pointer to start of parameter data, PTR_ERR otherwise. */ void *dfh_find_param(struct dfl_device *dfl_dev, int param_id, unsigned *pver, unsigned *pcount) > >> >>> >>>> + */ >>>> +u64 *dfh_find_param(struct dfl_device *dfl_dev, int param_id) >>>> +{ >>>> + return find_param(dfl_dev->params, dfl_dev->param_size, param_id); >>>> +} >>>> +EXPORT_SYMBOL_GPL(dfh_find_param); >>> >>> ... >>> >>>> + finfo = kzalloc(sizeof(*finfo) + dfh_psize, GFP_KERNEL); >>> >>> It sounds like a candidate for struct_size() from overflow.h. >>> I.o.w. check that header and come up with the best what can >>> suit your case. >> >> finfo = kzalloc(struct_size(finfo, params, dfh_psize/sizeof(u64)), >> GFP_KERNEL); >> >> Does seem better. > > How about we change the dfh_get_psize() to like dfh_get_pcount(), so we > don't have to multiply & divide back and forth. We need the size in bytes for calls to kmemdup, devm_kmemdup, and memcpy_fromio, but we only need to divide once here. > > Or we just use size_add()? I think using struct_size is better because the params member of struct dfl_feature_info is a trailing flexible array. Thanks for the feedback, Matthew > > Thanks, > Yilun > >> >> Thanks for the suggestion, >> Matthew Gerlach >> >> >>> >>>> if (!finfo) >>>> return -ENOMEM; >>> >>> -- >>> With Best Regards, >>> Andy Shevchenko >>> >>> >>> >
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