On Tue, Feb 09, 2021 at 03:28:16PM +0000, Gustavo Pimentel wrote: > On Mon, Feb 8, 2021 at 22:53:54, Krzysztof Wilczyński <kw@xxxxxxxxx> > wrote: > > [...] > > > Thanks for your review. I will wait for a couple of days, before sending > > > a new version of this patch series based on your feedback. > > > > Thank you! > > > > There might be one more change, and improvement, to be done as per > > Bjorn's feedback, see: > > > > https://urldefense.com/v3/__https://lore.kernel.org/linux-pci/20210208193516.GA406304@bjorn-Precision-5520/__;!!A4F2R9G_pg!Oxp56pU_UN6M2BhfNRSdYqsFUncqVklBj_1IdLQD_w_V6dKRPDO_FjPUystMa5D39SRj8uo$ > > > > The code in question would be (exceprt from the patch): > > > > [...] > > +static int dw_xdata_pcie_probe(struct pci_dev *pdev, > > + const struct pci_device_id *pid) > > +{ > > + const struct dw_xdata_pcie_data *pdata = (void *)pid->driver_data; > > + struct dw_xdata *dw; > > [...] > > + dw->rg_region.vaddr = pcim_iomap_table(pdev)[pdata->rg_bar]; > > + if (!dw->rg_region.vaddr) > > + return -ENOMEM; > > [...] > > > > Perhaps something like the following would would? > > > > void __iomem * const *iomap_table; > > > > iomap_table = pcim_iomap_table(pdev); > > if (!iomap_table) > > return -ENOMEM; > > > > dw->rg_region.vaddr = iomap_table[pdata->rg_bar]; > > if (!dw->rg_region.vaddr) > > return -ENOMEM; > > > > With sensible error messages added, of course. What do you think? > > I think all the improvements are welcome. I will do that. > My only doubt is if Bjorn recommends removing the > iomap_table[pdata->rg_bar] check, after adding the verification on the > pcim_iomap_table, because all other drivers doesn't do that. I misunderstood the usage of pcim_iomap_table() -- it looks like one must call pcim_iomap_regions() *first*, and test its result, and *that* is where we should catch any pcim_iomap_table() failures, e.g., rc = pcim_iomap_regions() # or pcim_iomap_regions_request_all() if (rc) return rc; # pcim_iomap_table() or other failure vaddr = pcim_iomap_table()[BAR]; if (!vaddr) return -ENOMEM; # BAR doesn't exist You *do* correctly call pcim_iomap_regions() first, which calls pcim_imap_table() internally, so if pcim_iomap_table() were to return NULL, you should catch it there. Then we assume that the subsequent "pcim_iomap_table()[BAR]" call will succeed and NOT return NULL, so it should be safe to index into the table. And if the table[BAR] entry is NULL, it means the BAR doesn't exist or isn't mapped. That sort of makes sense, but the API design doesn't quite seem obviously correct to me. The table was created by pcim_iomap_regions(), and pcim_iomap_table() is basically retrieving that artifact. I wonder if it could be improved by making pcim_iomap_table() strictly internal to devres.c and having the pcim_iomap functions return the table directly. Then the code would look something like this: table = pcim_iomap_regions(); if (IS_ERR(table)) return PTR_ERR(table); # pcim_iomap_table() or other failure vaddr = table[BAR]; # "table" is guaranteed to be non-NULL if (!vaddr) return -ENOMEM; Obviously this is not something you should do for *this* series. I think you should follow the example of other drivers, which means keeping your patch exactly as you posted it. I'm just interested in opinions on this as a possible future API improvement. Bjorn
