[RFC PATCH v1 34/57] sata_sil24: Remove PAGE_SIZE compile-time constant assumption

Ryan Roberts
2024-10-14T12:11:56Z

To prepare for supporting boot-time page size selection, refactor code
to remove assumptions about PAGE_SIZE being compile-time constant. Code
intended to be equivalent when compile-time page size is active.

Convert "struct sil24_ata_block" and "struct sil24_atapi_block" to use a
flexible array member for their sge[] array. The previous static size of
SIL24_MAX_SGE depends on PAGE_SIZE so doesn't work for boot-time page
size.

Wrap global variables that are initialized with PAGE_SIZE derived values
using DEFINE_GLOBAL_PAGE_SIZE_VAR() so their initialization can be
deferred for boot-time page size builds.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---

***NOTE***
Any confused maintainers may want to read the cover note here for context:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

drivers/ata/sata_sil24.c | 46 +++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 72c03cbdaff43..85c6382976626 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -42,26 +42,25 @@ struct sil24_sge {
__le32 flags;
};

+/*
+ * sil24 fetches in chunks of 64bytes. The first block
+ * contains the PRB and two SGEs. From the second block, it's
+ * consisted of four SGEs and called SGT. Calculate the
+ * number of SGTs that fit into one page.
+ */
+#define SIL24_PRB_SZ (sizeof(struct sil24_prb) + 2 * sizeof(struct sil24_sge))
+#define SIL24_MAX_SGT ((PAGE_SIZE - SIL24_PRB_SZ) / (4 * sizeof(struct sil24_sge)))
+
+/*
+ * This will give us one unused SGEs for ATA. This extra SGE
+ * will be used to store CDB for ATAPI devices.
+ */
+#define SIL24_MAX_SGE (4 * SIL24_MAX_SGT + 1)

enum {
SIL24_HOST_BAR = 0,
SIL24_PORT_BAR = 2,

- /* sil24 fetches in chunks of 64bytes. The first block
- * contains the PRB and two SGEs. From the second block, it's
- * consisted of four SGEs and called SGT. Calculate the
- * number of SGTs that fit into one page.
- */
- SIL24_PRB_SZ = sizeof(struct sil24_prb)
- + 2 * sizeof(struct sil24_sge),
- SIL24_MAX_SGT = (PAGE_SIZE - SIL24_PRB_SZ)
- / (4 * sizeof(struct sil24_sge)),
-
- /* This will give us one unused SGEs for ATA. This extra SGE
- * will be used to store CDB for ATAPI devices.
- */
- SIL24_MAX_SGE = 4 * SIL24_MAX_SGT + 1,
-
/*
* Global controller registers (128 bytes @ BAR0)
*/
@@ -244,13 +243,13 @@ enum {

struct sil24_ata_block {
struct sil24_prb prb;
- struct sil24_sge sge[SIL24_MAX_SGE];
+ struct sil24_sge sge[];
};

struct sil24_atapi_block {
struct sil24_prb prb;
u8 cdb[16];
- struct sil24_sge sge[SIL24_MAX_SGE];
+ struct sil24_sge sge[];
};

union sil24_cmd_block {
@@ -373,7 +372,7 @@ static struct pci_driver sil24_pci_driver = {
#endif
};

-static const struct scsi_host_template sil24_sht = {
+static DEFINE_GLOBAL_PAGE_SIZE_VAR_CONST(struct scsi_host_template, sil24_sht, {
__ATA_BASE_SHT(DRV_NAME),
.can_queue = SIL24_MAX_CMDS,
.sg_tablesize = SIL24_MAX_SGE,
@@ -382,7 +381,7 @@ static const struct scsi_host_template sil24_sht = {
.sdev_groups = ata_ncq_sdev_groups,
.change_queue_depth = ata_scsi_change_queue_depth,
.device_configure = ata_scsi_device_configure
-};
+});

static struct ata_port_operations sil24_ops = {
.inherits = &sata_pmp_port_ops,
@@ -1193,7 +1192,7 @@ static int sil24_port_start(struct ata_port *ap)
struct device *dev = ap->host->dev;
struct sil24_port_priv *pp;
union sil24_cmd_block *cb;
- size_t cb_size = sizeof(*cb) * SIL24_MAX_CMDS;
+ size_t cb_size = PAGE_SIZE * SIL24_MAX_CMDS;
dma_addr_t cb_dma;

pp = devm_kzalloc(dev, sizeof(*pp), GFP_KERNEL);
@@ -1258,7 +1257,6 @@ static void sil24_init_controller(struct ata_host *host)

static int sil24_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
{
- extern int __MARKER__sil24_cmd_block_is_sized_wrongly;
struct ata_port_info pi = sil24_port_info[ent->driver_data];
const struct ata_port_info *ppi[] = { &pi, NULL };
void __iomem * const *iomap;
@@ -1266,9 +1264,9 @@ static int sil24_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
int rc;
u32 tmp;

- /* cause link error if sil24_cmd_block is sized wrongly */
- if (sizeof(union sil24_cmd_block) != PAGE_SIZE)
- __MARKER__sil24_cmd_block_is_sized_wrongly = 1;
+ /* union sil24_cmd_block must be PAGE_SIZE */
+ BUG_ON(struct_size_t(struct sil24_atapi_block, sge, SIL24_MAX_SGE) != PAGE_SIZE);
+ BUG_ON(struct_size_t(struct sil24_ata_block, sge, SIL24_MAX_SGE) > PAGE_SIZE);

ata_print_version_once(&pdev->dev, DRV_VERSION);

--
2.43.0