linux-kernel - Re: [PATCH 22/24] thunderbolt: Add support for host and device NVM firmware upgrade

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Date:   Thu, 25 May 2017 17:39:40 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Amir Levy <amir.jer.levy@...el.com>,
        Andy Lutomirski <luto@...nel.org>, Mario.Limonciello@...l.com,
        Jared.Dominguez@...l.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/24] thunderbolt: Add support for host and device NVM
 firmware upgrade

On Thu, May 25, 2017 at 03:28:34PM +0200, Greg Kroah-Hartman wrote:
> On Thu, May 18, 2017 at 05:39:12PM +0300, Mika Westerberg wrote:
> > +static int tb_switch_nvm_add(struct tb_switch *sw)
> > +{
> > +	struct nvmem_device *nvm_dev;
> > +	struct tb_switch_nvm *nvm;
> > +	u32 val;
> > +	int ret;
> > +
> > +	if (!sw->dma_port)
> > +		return 0;
> > +
> > +	nvm = kzalloc(sizeof(*nvm), GFP_KERNEL);
> > +	if (!nvm)
> > +		return -ENOMEM;
> > +
> > +	nvm->id = ida_simple_get(&nvm_ida, 0, 0, GFP_KERNEL);
> > +
> > +	/*
> > +	 * If the switch is in safe-mode the only accessible portion of
> > +	 * the NVM is the non-active one where userspace is expected to
> > +	 * write new functional NVM.
> > +	 */
> > +	if (!sw->safe_mode) {
> > +		u32 nvm_size, hdr_size;
> > +
> > +		ret = dma_port_flash_read(sw->dma_port, NVM_FLASH_SIZE, &val,
> > +					  sizeof(val));
> > +		if (ret)
> > +			goto err_ida;
> > +
> > +		hdr_size = sw->generation < 3 ? SZ_8K : SZ_16K;
> > +		nvm_size = (SZ_1M << (val & 7)) / 8;
> > +		nvm_size = (nvm_size - hdr_size) / 2;
> > +
> > +		ret = dma_port_flash_read(sw->dma_port, NVM_VERSION, &val,
> > +					  sizeof(val));
> > +		if (ret)
> > +			goto err_ida;
> > +
> > +		nvm->major = val >> 16 & 0xff;
> > +		nvm->minor = val >> 8 & 0xff;
> > +
> > +		nvm_dev = register_nvmem(sw, nvm->id, nvm_size, true);
> > +		if (IS_ERR(nvm_dev)) {
> > +			ret = PTR_ERR(nvm_dev);
> > +			goto err_ida;
> > +		}
> > +		nvm->active = nvm_dev;
> > +	}
> > +
> > +	nvm_dev = register_nvmem(sw, nvm->id, NVM_MAX_SIZE, false);
> > +	if (IS_ERR(nvm_dev)) {
> > +		ret = PTR_ERR(nvm_dev);
> > +		goto err_nvm_active;
> > +	}
> > +	nvm->non_active = nvm_dev;
> > +
> > +	sw->nvm = nvm;
> > +
> > +	ret = sysfs_create_group(&sw->dev.kobj, &nvm_group);
> 
> Why are you adding this to the sw device?  And doing so _after_ it was
> announced to userspace?  Why can't you make it part of the device's
> default groups so that the driver core can handle it properly?

I was thinking those attributes should show up only when we have
successfully created the two NVMem devices. But maybe I can add those
conditionally to the device default groups and make the attributes
return error if the NVM device creation fails.

> Hint, if you ever have to call sysfs_* from within a driver, something
> might really be wrong :)

Understood, thanks.