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====== Michael Decker: Driver Development ======
==== Week A ====
----

=== 30 July ===

This is my first entry for week A.  As you can see, I've decided to go hex with my week numbers.  This is because I'm just that cool.

It's been a few days since my last journal entry, so let's have a quick **state of the code** address.  Within my repository, you'll find the //eepro100// branch and the //skge// branch.

The **eepro100** is now stable according to testing by mdc and myself.  This driver was converted from the Etherboot version.  It was then transformed a great deal into a mostly new beast.  I've identified one issue the Linux driver addresses which the gPXE driver does not - that is a rare rx-hang bug in an 82559B-based NIC.  This is addressable by owners via an EEPROM update, however.

The **skge** is not yet stable.  Testing with DOS over AoE, I haven't encountered any problems.  However, mdc has found some intermittent problems with this driver with iSCSI.  This driver is a stripped-down version of the Linux driver.  I don't have any datasheet for this device, and haven't reproduced the error, so debugging is .. difficult.

I converted the **atlx** Linux driver in hopes of supporting the Attansic L2 on-board NIC on my test machine.  However, it seems this driver may not fully support the L2 as of yet.  I don't have an L1 to test this with, so I have abandoned this code for now.  I decided to push it anyway, as someone else may find my hard work useful.  Who knows, it may just work with an L1 as-is.  All removed code is just commented out, so it will be easy to modify.

  * [[http://git.etherboot.org/?p=people/mdeck/gpxe.git;a=shortlog;h=atlx|atlx driver added, gPXE migration]]

I have a few **3c905**-based NICs to work with here.  There is an existing Etherboot driver for these cards, but mdc said that driver is no good. He gave the go-ahead to convert the Linux driver for these cards, so that is next on my plate.

=== 31 July ===

The **3c905** is under development.  Two commits have been made.  The Linux driver was added:
  * [[http://git.etherboot.org/?p=people/mdeck/gpxe.git;a=commit;h=45b653bf7fc31207e7755d8ed0cc029c7ff5ba45|[Drivers-3c59x] 3c59x Linux driver added]]
Transition from Linux to gPXE API is in-progress:
  * [[http://git.etherboot.org/?p=people/mdeck/gpxe.git;a=commit;h=02ce4088910dc2fef14752eca305c6791d15318c|[Drivers-3c59x] linux -> gPXE API changes]]
This is a sizable driver, and progress is slow and steady.  I've already converted a Linux driver twice before, so I have a list of changes to follow.  I posted these in a //soc-mentors// email, but I'll post them here for others to reference:
<file>
The following functions were replaced with nothing:
    pci_unmap_addr_set
    pci_unmap_len_set
    pci_unmap_single
    pci_unmap_page
    pci_dma_sync_single_for_cpu
    pci_dma_sync_single_for_device
    netif_tx_lock_bh
    netif_tx_unlock_bh
    skb_padto(skb,ETH_ZLEN) (io_buffer already pads)
    netif_stop_queue
    netif_msg_X
    netif_wake_queue
    netif_queue_stopped
    __netif_rx_complete
    spin_lock_irqsave
    spin_unlock_irqrestore
    netif_napi_add
    spin_lock_bh
    spin_unlock_bh
    napi_enable (after open() will enable polling)
    spin_lock_irq
    spin_unlock_irq
    pci_release_regions
    pci_disable_device

The following features were considered unneeded and relevant code was omitted:
    wol
    ethtool
    tx/rx checksum offload
    jumbo frames
    skb fragments
    power management

The following function replacements were made:
    pci_alloc_consistent
        malloc_dma, virt_to_phys, memset
    pci_free_consistent
        free_dma
    pci_map_single
        virt_to_phys
    smp_wmb
        wmb
    netif_running
        mostly nothing, a few netdev_link_ok
    netif_receive_skb
        netdev_rx
    netif_carrier_off
        netdev_link_down
    skb_copy_from_linear_data
        memcpy
    netdev_alloc_skb
        alloc_iob, memset
    kcalloc
        malloc_dma, memset
    dev_kfree_skb
        free_iob
    kzalloc
        malloc_dma, memset
</file>

This is not an all-inclusive list, as I have already made some replacements that I haven't added here.  I will update the list as I have time to review the code.

Also, the **skge** driver was updated.  Linux performs a memory clear during ''pci_alloc_consistent'' and ''netdev_alloc_skb'', which I hadn't duplicated.
  * [[http://git.etherboot.org/?p=people/mdeck/gpxe.git;a=commitdiff;h=9d20ad0a66c1303e16cb2d9c88a9a330c76d0750|[Drivers-skge] Added memory clearing following allocations]]
  * [[http://git.etherboot.org/?p=people/mdeck/gpxe.git;a=commitdiff;h=0c25964551adf15c9e541efaee967038a7e4315a|[Drivers-skge] Fix previous commit]]

My next goal is to get the **3c59x** running.  This shouldn't be more than a few days of hard work if no problems are encountered.
Trace: • week5 • project_plan • ideas • mdeck • week10 • week8 • week0 • week3 • week1 • week5 • bootovernfs • iscsi • dhcp_-_build_instructions • ubuntu910