netdev - RE: [net-2.6 PATCH 6/10] Neterion: New driver: Hardware init & configuration

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Date:	Mon, 16 Mar 2009 23:25:19 -0400
From:	"Ramkrishna Vepa" <Ramkrishna.Vepa@...erion.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	"Netdev" <netdev@...r.kernel.org>,
	"David Miller" <davem@...emloft.net>,
	"Jeff Garzik" <jgarzik@...ox.com>
Subject: RE: [net-2.6 PATCH 6/10] Neterion: New driver: Hardware init & configuration

Andi,

Thanks for the comments. We are looking into them.

Question of the following -
> In general your driver looks like it could use a pass with sparse's
> __iomem checking (make V=1)
How do I enable this checking?

Ram

> > +struct __hw_channel*
> > +__hw_channel_allocate(
> > +	struct __hw_device *hldev,
> > +	struct __hw_vpath_handle *vph,
> > +	enum __hw_channel_type type,
> > +	u32 length,
> > +	u32 alloc_work_array,
> > +	u32 alloc_free_array,
> > +	u32 alloc_reserve_array,
> > +	u32 per_dtr_space,
> > +	void *userdata)
> 
> Having so many arguments in a function is usually a clear sign that it
> needs
> to be refactored into smaller functions.
> 
> > +	channel = (struct __hw_channel *) vmalloc(size);
> 
> You seem to use vmalloc nearly everywhere. First that has a lot of
> overhead (rounds up to pages, flushes TLBs) and also will cause more
> TLB misses. It's better to avoid it when not absolutely needed.
> 
> > +	vxge_assert(channel != NULL);
> > +
> > +	hldev = (struct __hw_device  *)channel->devh;
> 
> That assert is pretyt pointless because you'll just get a NULL pointer
> reference next. Same true all over. asserts (or rather BUG_ON) only
> make sense when they check for something that's not nearly obvious
> given a oops.
> 
> > +	while (next_ptr != 0) {
> > +
> > +		cap_id = VXGE_HW_PCI_CAP_ID((((u8 *)pci_config)  +
> next_ptr));
> > +
> > +		switch (cap_id) {
> > +
> > +		case VXGE_HW_PCI_CAP_ID_PM:
> > +			hldev->pci_caps.pm_cap_offset = next_ptr;
> 
> This all could be done much shorter with a table.
> 
> > +	if (VXGE_HW_PCI_CONFIG_SPACE_SIZE <= 0x100)
> > +		goto exit;
> > +
> > +	next_ptr = 0x100;
> 
> Such magic numbers are frowned upon.
> 
> Also in general you should use the pci capabilities accessor functions
> provided by the PCI layer.
> 
> 
> > +			break;
> > +		case VXGE_HW_PCI_EXT_CAP_ID_DSN:
> > +			hldev->pci_e_ext_caps.dsn_cap_offset = next_ptr;
> > +			break;
> > +		case VXGE_HW_PCI_EXT_CAP_ID_PWR:
> > +			hldev->pci_e_ext_caps.pwr_budget_cap_offset =
next_ptr;
> > +			break;
> > +
> > +		default:
> > +
> > +			break;
> > +		}
> > +
> > +		next_ptr = (u16)VXGE_HW_PCI_EXT_CAP_NEXT(
> > +				*(u32 *)(((u8 *)pci_config)  +
next_ptr));
> 
> Especially the patch orgies are scary. Does that really use readl()
et.al.
> correctly? I doubt it. Again this should use the pci layer code for
this.
> 
> > +/**
> > + * vxge_hw_device_private_set - Set driver context.
> > + * @hldev: HW device handle.
> > + * @data: pointer to driver context
> > + *
> > + * Use HW device to set driver context.
> > + *
> > + * See also: vxge_hw_device_private_get()
> > + */
> > +void vxge_hw_device_private_set(struct __hw_device *hldev, void
*data)
> > +{
> > +	hldev->upper_layer_data = data;
> > +}
> 
> Such wrappers are not encouraged in Linux code, which aims to do with
> only necessary abstraction. Lots of occurrences.
> 
> > +
> > +#ifdef VXGE_HW_INTERNAL_COMPILER_ERROR
> > +
> > +#pragma optimize("", off)
> > +
> > +#endif
> 
> That's not for gcc isn't it?
> 
> > +/*
> > + * __hw_ring_block_memblock_idx - Return the memblock index
> > + * @block: Virtual address of memory block
> > + *
> > + * This function returns the index of memory block
> > + */
> > +static inline u32
> > +__hw_ring_block_memblock_idx(
> > +	u8 (block)[VXGE_HW_BLOCK_SIZE])
> > +{
> > +	return (u32)*((u64 *)((u8 *)block  +
> > +		VXGE_HW_RING_MEMBLOCK_IDX_OFFSET));
> 
> Is that readl/writel clean again?
> 
> In general your driver looks like it could use a pass with sparse's
> __iomem checking (make V=1)
> 
> > +static enum vxge_hw_status
> > +__hw_ring_mempool_item_alloc(
> > +	struct vxge_hw_mempool *mempoolh,
> > +	void *memblock,
> > +	u32 memblock_index,
> > +	struct vxge_hw_mempool_dma *dma_object,
> > +	void *item,
> > +	u32 index,
> > +	u32 is_last,
> > +	void *userdata)
> 
> Again far too many arguments.
> 
> 
> Stopped reading for now, but that file needs a lot of work in general.
> 
> -Andi
> 
> 
> --
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