linux-kernel - Re: [PATCH RFC 05/15] ims-msi: Add mask/unmask routines

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Date:   Sat, 25 Apr 2020 23:49:44 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Jiang <dave.jiang@...el.com>, vkoul@...nel.org,
        megha.dey@...ux.intel.com, maz@...nel.org, bhelgaas@...gle.com,
        rafael@...nel.org, gregkh@...uxfoundation.org, hpa@...or.com,
        alex.williamson@...hat.com, jacob.jun.pan@...el.com,
        ashok.raj@...el.com, jgg@...lanox.com, yi.l.liu@...el.com,
        baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com,
        tony.luck@...el.com, jing.lin@...el.com, dan.j.williams@...el.com,
        kwankhede@...dia.com, eric.auger@...hat.com, parav@...lanox.com
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-pci@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH RFC 05/15] ims-msi: Add mask/unmask routines

Dave Jiang <dave.jiang@...el.com> writes:
>  
> +static u32 __dev_ims_desc_mask_irq(struct msi_desc *desc, u32 flag)

...mask_irq()? This is doing both mask and unmask depending on the
availability of the ops callbacks. 

> +{
> +	u32 mask_bits = desc->platform.masked;
> +	const struct platform_msi_ops *ops;
> +
> +	ops = desc->platform.msi_priv_data->ops;
> +	if (!ops)
> +		return 0;
> +
> +	if (flag) {

flag? Darn, this has a clear boolean meaning of mask or unmask and 'u32
flag' is the most natural and obvious self explaining expression for
this, right?

> +		if (ops->irq_mask)
> +			mask_bits = ops->irq_mask(desc);
> +	} else {
> +		if (ops->irq_unmask)
> +			mask_bits = ops->irq_unmask(desc);
> +	}
> +
> +	return mask_bits;

What's mask_bits? This is about _ONE_ IMS interrupt. Can it have
multiple mask bits and if so then the explanation which I decoded by
crystal ball probably looks like this:

Bit  0:  Don't know whether it's masked
Bit  1:  Perhaps it's masked
Bit  2:  Probably it's masked
Bit  3:  Mostly masked
...
Bit 31:  Fully masked

Or something like that. Makes a lot of sense in a XKCD cartoon at least.

> +}
> +
> +/**
> + * dev_ims_mask_irq - Generic irq chip callback to mask IMS interrupts
> + * @data: pointer to irqdata associated to that interrupt
> + */
> +static void dev_ims_mask_irq(struct irq_data *data)
> +{
> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
> +
> +	desc->platform.masked = __dev_ims_desc_mask_irq(desc, 1);

The purpose of this masked information is?

Thanks,

        tglx