linux-kernel - Re: [PATCH v4 2/3] PCI: dwc: ep: Add per-PF BAR and inbound ATU mapping support

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Message-ID: <8202cb0f-3d04-449e-ac37-181afbb35fa1@ti.com>
Date: Fri, 30 Jan 2026 16:09:26 +0530
From: Aksh Garg <a-garg7@...com>
To: Niklas Cassel <cassel@...nel.org>
CC: Koichiro Den <den@...inux.co.jp>, <linux-pci@...r.kernel.org>,
	<jingoohan1@...il.com>, <mani@...nel.org>, <lpieralisi@...nel.org>,
	<kwilczynski@...nel.org>, <robh@...nel.org>, <bhelgaas@...gle.com>,
	<Zhiqiang.Hou@....com>, <gustavo.pimentel@...opsys.com>,
	<linux-kernel@...r.kernel.org>, <s-vadapalli@...com>, <danishanwar@...com>
Subject: Re: [PATCH v4 2/3] PCI: dwc: ep: Add per-PF BAR and inbound ATU
 mapping support



On 30/01/26 15:23, Niklas Cassel wrote:
> On Fri, Jan 30, 2026 at 09:42:43AM +0530, Aksh Garg wrote:
>> On 29/01/26 19:44, Niklas Cassel wrote:
>> > On Thu, Jan 29, 2026 at 02:47:52PM +0530, Aksh Garg wrote:
>> > > -static void dw_pcie_ep_clear_ib_maps(struct dw_pcie_ep *ep, enum pci_barno bar)
>> > > +static void dw_pcie_ep_clear_ib_maps(struct dw_pcie_ep *ep, u8 func_no, enum pci_barno bar)
>> > >  {
>> > > +	struct dw_pcie_ep_func *ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
>> > >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>> > >  	struct device *dev = pci->dev;
>> > >  	unsigned int i, num;
>> > > @@ -152,18 +157,18 @@ static void dw_pcie_ep_clear_ib_maps(struct dw_pcie_ep *ep, enum pci_barno bar)
>> > >  	u32 *indexes;
>> > 
>> > Hello Aksh,
>> > 
>> > Considering that all other functions that you have modified, you have added a:
>> > 
>> > if (!ep_func)
>> > 	return;
>> > 
>> > 
>> > I think you should do the same to this function.
>> > 
>> 
>> I omitted this NULL check here because all the current call sites of
>> dw_pcie_ep_clear_ib_maps() already perform this validation. I felt
>> adding it here would add redundancy in the code.
> 
> Ok, but with that logic, shouldn't we also remove the NULL checks from
> dw_pcie_ep_ib_atu_bar() and dw_pcie_ep_ib_atu_addr(), because they are
> only called from dw_pcie_ep_set_bar(), which already has the ep_func
> NULL check?
> 

Yes, that's correct. Alternatively, we can add the NULL check in
dw_pcie_ep_clear_ib_maps() as well, making all the functions using
ep_func self-contained and defensive, removing the dependency on whether
the callers perform NULL checks. This makes the code more future proof,
as new callers won't need to be aware of the NULL pointer possibility.

Please provide your views on this approach.

> 
> Kind regards,
> Niklas
>